diff --git a/onnxruntime/contrib_ops/contrib_ops.cc b/onnxruntime/contrib_ops/contrib_ops.cc
index ad52918ab7..c2c8d3318d 100644
--- a/onnxruntime/contrib_ops/contrib_ops.cc
+++ b/onnxruntime/contrib_ops/contrib_ops.cc
@@ -92,6 +92,36 @@ Sample echo operator.)DOC");
       .TypeAndShapeInferenceFunction(ONNX_NAMESPACE::propagateShapeAndTypeFromFirstInput)
       .SetDoc(R"DOC(Returns which elements of the input are NaN.)DOC");
 
+  ONNX_CONTRIB_OPERATOR_SCHEMA(Tokenizer)
+      .SetDomain(kMSDomain)
+      .SinceVersion(1)
+      .Input(0, "X", "Strings to tokenize", "T")
+      .Output(0, "Y", "Tokenized strings", "T")
+      .TypeConstraint(
+          "T",
+          {"tensor(string)"},
+          "Input/Output is a string tensor")
+      .Attr(
+          "mark",
+          "Boolean whether to mark the beginning/end character with start of text character (0x02)/end of text character (0x03).",
+          AttributeProto::INT)
+      .Attr(
+          "pad_value",
+          "The string used to pad output tensors when the tokens extracted doesn't match the maximum number of tokens found. If start/end markers are needed, padding will appear outside the markers.",
+          AttributeProto::STRING)
+      .Attr(
+          "separators",
+          "The list of separators, two consecutive segments in X connected by a separator would be divided into two tokens.",
+          AttributeProto::STRINGS)
+      .Attr(
+          "mincharnum",
+          "Minimum number of characters allowed in the output. For example, if mincharnum is 2, tokens such as \"A\" and \"B\" would be ignored",
+          AttributeProto::INT)
+      .TypeAndShapeInferenceFunction([](ONNX_NAMESPACE::InferenceContext& ctx) {
+        propagateElemTypeFromInputToOutput(ctx, 0, 0);
+      })
+      .SetDoc(R"DOC(Tokenizer divides each string in X into a vector of strings along the last axis. All input strings including attributes are UTF-8 encoded.)DOC");
+
   // Operators for linear 8 bit quanitzation support.
   ONNX_CONTRIB_OPERATOR_SCHEMA(QuantizeLinear)
       .SetDomain(kMSDomain)
@@ -491,6 +521,7 @@ class ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1,
 class ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, float, ExpandDims);
 class ONNX_OPERATOR_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, AttnLSTM);
 class ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, float, IsNaN);
+class ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, string, Tokenizer);
 class ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, uint8_t, DequantizeLinear);
 class ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, int8_t, DequantizeLinear);
 class ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, float, QuantizeLinear);
@@ -505,6 +536,7 @@ void RegisterContribKernels(std::function<void(KernelCreateInfo&&)> fn) {
   fn(BuildKernel<ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, float, ExpandDims)>());
   fn(BuildKernel<ONNX_OPERATOR_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, AttnLSTM)>());
   fn(BuildKernel<ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, float, IsNaN)>());
+  fn(BuildKernel<ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, string, Tokenizer)>());
   fn(BuildKernel<ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, uint8_t, DequantizeLinear)>());
   fn(BuildKernel<ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, int8_t, DequantizeLinear)>());
   fn(BuildKernel<ONNX_OPERATOR_TYPED_KERNEL_CLASS_NAME(kCpuExecutionProvider, kMSDomain, 1, float, QuantizeLinear)>());
diff --git a/onnxruntime/contrib_ops/cpu/tokenizer.cc b/onnxruntime/contrib_ops/cpu/tokenizer.cc
new file mode 100644
index 0000000000..7e83e1ca71
--- /dev/null
+++ b/onnxruntime/contrib_ops/cpu/tokenizer.cc
@@ -0,0 +1,489 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#include "tokenizer.h"
+#include "onnx/defs/schema.h"
+#include "core/common/common.h"
+#include "core/framework/tensor.h"
+
+#include "core/common/utf8_util.h"
+
+#include <codecvt>
+#include <locale>
+
+namespace onnxruntime {
+namespace contrib {
+
+using namespace utf8_util;
+
+ONNX_CPU_OPERATOR_TYPED_MS_KERNEL(
+    Tokenizer,
+    1,
+    string,
+    KernelDefBuilder()
+        .TypeConstraint("T", DataTypeImpl::GetTensorType<std::string>()),
+    contrib::Tokenizer);
+
+namespace tokenizer_details {
+
+const char start_text = 0x2;
+const char end_text = 0x3;
+
+const std::string conv_error("Conversion Error");
+const std::wstring wconv_error(L"Conversion Error");
+
+// Use a Trie like structure for searching multiple strings
+// at once but convert it to a ternary tree for saving space.
+// We insert separators in the same order they are specified.
+// Template parameter is a CharT which can be a char/wchar_t
+// or anything else that supports operator ><,== as long as
+// this is not a variable length sequence. We convert utf8 to utf16
+// before inserting.
+// Value is a supplementary information useful for search hit
+// and is present in the nodes that terminate the whole search pattern
+template <class CharT, class Value>
+class TernarySearchTree {
+ private:
+  struct Node {
+    std::unique_ptr<Node> left_;
+    std::unique_ptr<Node> mid_;
+    std::unique_ptr<Node> right_;
+    CharT c_;  // character
+    Value value_;
+    bool has_val_;
+
+    explicit Node(CharT c) : c_(c), value_(), has_val_(false) {
+    }
+    ~Node() = default;
+  };
+
+  struct GetState {
+    const CharT* const str_;
+    const size_t len_;
+    size_t depth_;
+    const Value* result_;
+  };
+
+ public:
+  TernarySearchTree() = default;
+  ~TernarySearchTree() = default;
+
+  /**
+  * Returns a ptr to an associated value and nullptr on search miss.
+  * Must use default constructed state.
+  */
+  const Value* get(const CharT* str, size_t len) const {
+    if (len == 0) {
+      return nullptr;
+    }
+    GetState get_state{str, len, 0, nullptr};
+    get(root_.get(), get_state);
+    return get_state.result_;
+  }
+
+  /**
+  * Returns true if successful and false on empty strings
+  * and duplicates.
+  */
+  bool put(const CharT* str, size_t len, const Value& v) {
+    if (len < 1) {
+      assert(false);
+      return false;
+    }
+    Node* new_root = put(root_.get(), str, len, v, 0);
+    if (new_root != nullptr) {
+      root_.release();
+      root_.reset(new_root);
+      return true;
+    }
+    return false;
+  }
+
+ private:
+  void update_state(const Node* node, GetState& state) const {
+    if (node->has_val_) {
+      if (state.result_ == nullptr) {
+        state.result_ = &node->value_;
+      } else if (node->value_ < *state.result_) {
+        state.result_ = &node->value_;
+      }
+    }
+  }
+  void get(const Node* node, GetState& state) const {
+    if (node == nullptr) {
+      return;
+    }
+    assert(state.depth_ < state.len_);
+    CharT c = state.str_[state.depth_];
+    if (c < node->c_) {
+      get(node->left_.get(), state);
+      return;
+    } else if (c > node->c_) {
+      get(node->right_.get(), state);
+      return;
+    } else if (state.depth_ < (state.len_ - 1)) {
+      // Check if we have a match at this node
+      update_state(node, state);
+      if (node->mid_ != nullptr) {
+        ++state.depth_;
+        get(node->mid_.get(), state);
+      }
+      return;
+    }
+    update_state(node, state);
+  }
+
+  Node* put(Node* node, const CharT* str, size_t len, const Value& v, size_t depth) {
+    CharT c = str[depth];
+
+    std::unique_ptr<Node> new_node;
+    if (node == nullptr) {
+      new_node.reset(new Node(c));
+    }
+
+    Node* new_link = nullptr;
+    Node* n = (node != nullptr) ? node : new_node.get();
+    if (c < n->c_) {
+      new_link = put(n->left_.get(), str, len, v, depth);
+      if (new_link != nullptr) {
+        n->left_.release();
+        n->left_.reset(new_link);
+      }
+    } else if (c > n->c_) {
+      new_link = put(n->right_.get(), str, len, v, depth);
+      if (new_link != nullptr) {
+        n->right_.release();
+        n->right_.reset(new_link);
+      }
+    } else if (depth < (len - 1)) {
+      new_link = put(n->mid_.get(), str, len, v, depth + 1);
+      if (new_link != nullptr) {
+        n->mid_.release();
+        n->mid_.reset(new_link);
+      }
+    } else {
+      if (!n->has_val_) {
+        n->value_ = v;
+        n->has_val_ = true;
+        new_link = n;
+      }
+    }
+    if (new_link != nullptr) {
+      new_node.release();
+      return n;
+    }
+    return nullptr;
+  }
+  std::unique_ptr<Node> root_;
+};
+
+// We store the length of the original pattern within the
+// Ternary Tree. This allows us to cut out the length of the matching
+// separator from the original string.
+struct SearchValue {
+  size_t w_len;
+  int priority_;
+  bool operator<(const SearchValue& o) const {
+    return priority_ < o.priority_;
+  }
+};
+
+}  // namespace tokenizer_details
+
+using namespace tokenizer_details;
+
+struct Tokenizer::SearchData {
+  TernarySearchTree<wchar_t, SearchValue> tst_;
+};
+
+Tokenizer::Tokenizer(const OpKernelInfo& info) : OpKernel(info) {
+  int64_t mark = 0;
+  auto status = info.GetAttr("mark", &mark);
+  ONNXRUNTIME_ENFORCE(status.IsOK(), "attribute mark is not set");
+  mark_ = mark != 0;
+
+  status = info.GetAttr("pad_value", &pad_value_);
+  ONNXRUNTIME_ENFORCE(status.IsOK(), "attribute pad_value is not set");
+
+  status = info.GetAttr("mincharnum", &mincharnum_);
+  ONNXRUNTIME_ENFORCE(status.IsOK(), "attribute mincharnum is not set");
+  ONNXRUNTIME_ENFORCE(mincharnum_ > 0, "attribute mincharnum must have a positive value");
+
+  std::vector<std::string> separators;
+  status = info.GetAttrs<std::string>("separators", separators);
+  ONNXRUNTIME_ENFORCE(status.IsOK(), "attribute separators is not set");
+  ONNXRUNTIME_ENFORCE(!separators.empty(), "Requires at least one separator");
+
+  char_tokenezation_ = (separators.size() == 1 &&
+                        separators[0].empty());
+
+  ONNXRUNTIME_ENFORCE(!char_tokenezation_ || mincharnum_ < 2,
+                      "mincharnum is too big for char level tokenezation");
+
+  // Create TST and insert separators
+  if (!char_tokenezation_) {
+    std::unique_ptr<SearchData> sd(std::make_unique<SearchData>());
+    std::wstring_convert<std::codecvt_utf8<wchar_t>> converter(conv_error, wconv_error);
+    int priority = 0;  // earlier search patterns get priority
+    for (const auto& sep : separators) {
+      ONNXRUNTIME_ENFORCE(!sep.empty(), "No empty separators allowed");
+      std::wstring wsep = converter.from_bytes(sep);
+      ONNXRUNTIME_ENFORCE(wsep != wconv_error, "Separator strings contains invalid utf8 chars");
+      bool result = sd->tst_.put(wsep.c_str(), wsep.length(), {wsep.length(), priority});
+      ONNXRUNTIME_ENFORCE(result, "duplicate separator detected");
+      ++priority;
+    }
+    search_data_.swap(sd);
+  }
+}
+
+// Make SearchData definition available for destruction
+Tokenizer ::~Tokenizer() {
+}
+
+Status Tokenizer::CharTokenize(OpKernelContext* ctx, size_t N, size_t C,
+                               const std::vector<int64_t>& input_dims) const {
+  // With char tokenzation we get as many tokens as the number of
+  // utf8 characters in the string. So for every string we calculate its character(utf8) length
+  // add padding and add start/end test separators if necessary
+  size_t max_tokens = 0;
+  auto X = ctx->Input<Tensor>(0);
+  auto const input_data = X->template Data<std::string>();
+  auto curr_input = input_data;
+  auto const last = input_data + N * C;
+  while (curr_input != last) {
+    const auto& s = *curr_input;
+    size_t tokens = 0;  // length in utf8 chars
+    if (!utf8_validate(reinterpret_cast<const unsigned char*>(s.data()), s.size(),
+                       tokens)) {
+      return Status(common::ONNXRUNTIME, common::INVALID_ARGUMENT,
+                    "Input string contains invalid utf8 chars: " + s);
+    }
+    if (mark_) {
+      tokens += 2;  // Start/end markers as separate tokens
+    }
+    max_tokens = std::max(max_tokens, tokens);
+    ++curr_input;
+  }
+
+  std::vector<int64_t> output_dims(input_dims);
+  // Check if we have no output due to apparently empty strings input.
+  if ((max_tokens - mark_ * 2) == 0) {
+    output_dims.push_back(0);
+    TensorShape output_shape(output_dims);
+    ctx->Output(0, output_shape);
+    return Status::OK();
+  }
+
+  output_dims.push_back(max_tokens);
+  TensorShape output_shape(output_dims);
+  auto output_tensor = ctx->Output(0, output_shape);
+  auto const output_data = output_tensor->template MutableData<std::string>();
+  size_t output_index = 0;
+  curr_input = input_data;
+  while (curr_input != last) {
+    const auto& s = *curr_input;
+    if (mark_) {
+      new (output_data + output_index) std::string(&start_text, 1);
+      ++output_index;
+    }
+    size_t tokens = 0;
+    const size_t str_len = s.size();
+    for (size_t token_idx = 0; token_idx < str_len;) {
+      size_t tlen = 0;
+      bool result = utf8_bytes(static_cast<unsigned char>(s[token_idx]), tlen);
+      assert(result);
+      (void)result;
+      assert(token_idx + tlen <= str_len);
+      new (output_data + output_index) std::string(s.substr(token_idx, tlen));
+      ++output_index;
+      token_idx += tlen;
+      ++tokens;
+    }
+    if (mark_) {
+      new (output_data + output_index) std::string(&end_text, 1);
+      ++output_index;
+    }
+    // Padding strings
+    assert(tokens + (mark_ * 2) <= max_tokens);
+    const size_t pads = max_tokens - (mark_ * 2) - tokens;
+    for (size_t p = 0; p < pads; ++p) {
+      new (output_data + output_index) std::string(pad_value_);
+      ++output_index;
+    }
+    ++curr_input;
+  }
+  return Status::OK();
+}
+
+Status Tokenizer::SeparatorTokenize(OpKernelContext* ctx,
+                                    size_t N, size_t C,
+                                    const std::vector<int64_t>& input_dims) const {
+  struct Match {
+    int priority_;
+    size_t offset_;
+    size_t size_;
+    // create a conflict for overlapping matches
+    // thus if they overlap neither is less than the other
+    // and they are considered equal
+    bool operator<(const Match& o) const {
+      return (offset_ + size_) <= o.offset_;
+    }
+  };
+
+  std::wstring_convert<std::codecvt_utf8<wchar_t>> converter(conv_error, wconv_error);
+  // Scan all strings and attempt to find separators in them
+  // collect all the output tokens here
+  size_t max_tokens = 0;
+  std::vector<std::vector<std::wstring>> tokenized_strings;
+  tokenized_strings.reserve(N * C);
+  auto X = ctx->Input<Tensor>(0);
+  auto const input_data = X->template Data<std::string>();
+  auto curr_input = input_data;
+  auto const last = input_data + N * C;
+  while (curr_input != last) {
+    const auto& s = *curr_input;
+    std::wstring wstr = converter.from_bytes(s);
+    if (wstr == wconv_error) {
+      return Status(common::ONNXRUNTIME, common::INVALID_ARGUMENT,
+                    "Invalid utf8 chars in the input: " + s);
+    }
+
+    std::set<Match> matches;
+    const wchar_t* ws = wstr.c_str();
+    size_t len_remaining = wstr.length();
+    size_t offset = 0;
+    while (len_remaining > 0) {
+      const auto* val = search_data_->tst_.get(ws, len_remaining);
+      if (val != nullptr) {
+        auto p = matches.insert({val->priority_, offset, val->w_len});
+        while (!p.second && val->priority_ < p.first->priority_) {
+          // if overlapping matches of the same pattern(priority), then
+          // the earlier match naturally wins
+          matches.erase(p.first);
+          p = matches.insert({val->priority_, offset, val->w_len});
+        }
+      }
+      ++ws;
+      ++offset;
+      --len_remaining;
+    }
+
+    // Tokenize
+    tokenized_strings.emplace_back();
+    auto& row_tokens = tokenized_strings.back();
+    row_tokens.reserve(matches.size() + 1);
+    ws = wstr.c_str();
+    offset = 0;
+    for (const auto& m : matches) {
+      assert(m.offset_ >= offset);
+      size_t sz = (m.offset_ - offset);
+      if (sz > 0 && sz >= size_t(mincharnum_)) {
+        row_tokens.emplace_back(ws, sz);
+      }
+      offset = m.offset_ + m.size_;
+      ws = wstr.c_str() + offset;
+    }
+    assert(offset <= wstr.length());
+    if (offset < wstr.length()) {
+      row_tokens.emplace_back(ws, wstr.length() - offset);
+    }
+
+    size_t tokens = row_tokens.size();
+    if (mark_) {
+      tokens += 2;  // Start/end markers as separate tokens
+    }
+    max_tokens = std::max(max_tokens, tokens);
+    ++curr_input;
+  }
+
+  std::vector<int64_t> output_dims(input_dims);
+  // Check if we have no output due to either empty input
+  // everything is a separator
+  if ((max_tokens - mark_ * 2) == 0) {
+    output_dims.push_back(0);
+    TensorShape output_shape(output_dims);
+    ctx->Output(0, output_shape);
+    return Status::OK();
+  }
+
+  output_dims.push_back(max_tokens);
+  TensorShape output_shape(output_dims);
+
+  auto output_tensor = ctx->Output(0, output_shape);
+  auto const output_data = output_tensor->template MutableData<std::string>();
+
+#ifdef _DEBUG
+  const size_t max_output_index = N * C * max_tokens;
+#endif
+  size_t output_index = 0;
+  for (auto& row : tokenized_strings) {
+#ifdef _DEBUG
+    size_t c_idx = output_index;
+#endif
+    if (mark_) {
+      new (output_data + output_index) std::string(&start_text, 1);
+      ++output_index;
+    }
+    // Output tokens for this row
+    for (auto& token : row) {
+      new (output_data + output_index) std::string(converter.to_bytes(token));
+      ++output_index;
+    }
+    if (mark_) {
+      new (output_data + output_index) std::string(&end_text, 1);
+      ++output_index;
+    }
+    const size_t pads = max_tokens - (mark_ * 2) - row.size();
+    for (size_t p = 0; p < pads; ++p) {
+      new (output_data + output_index) std::string(pad_value_);
+      ++output_index;
+    }
+#ifdef _DEBUG
+    assert(output_index <= max_output_index);
+    assert((output_index - c_idx) <= max_tokens);
+#endif
+  }
+  return Status::OK();
+}
+
+Status Tokenizer::Compute(OpKernelContext* ctx) const {
+  // Get input buffer ptr
+  auto X = ctx->Input<Tensor>(0);
+  if (X->DataType() != DataTypeImpl::GetType<std::string>()) {
+    return Status(common::ONNXRUNTIME, common::INVALID_ARGUMENT,
+                  "tensor(string) expected as input");
+  }
+
+  auto& input_dims = X->Shape().GetDims();
+  size_t N = 0;
+  size_t C = 0;
+  if (input_dims.size() == 1) {
+    N = 1;
+    if (input_dims[0] < 1) {
+      return Status(common::ONNXRUNTIME, common::INVALID_ARGUMENT,
+                    "Invalid C dimension value");
+    }
+    C = input_dims[0];
+  } else if (input_dims.size() == 2) {
+    if (input_dims[0] < 1 || input_dims[1] < 1) {
+      return Status(common::ONNXRUNTIME, common::INVALID_ARGUMENT,
+                    "Invalid N and/or C dimension values");
+    }
+    N = input_dims[0];
+    C = input_dims[1];
+  } else {
+    return Status(common::ONNXRUNTIME, common::INVALID_ARGUMENT,
+                  "Input dimensions are either [C] or [N][C] allowed");
+  }
+
+  Status s;
+  if (char_tokenezation_) {
+    s = CharTokenize(ctx, N, C, input_dims);
+  } else {
+    s = SeparatorTokenize(ctx, N, C, input_dims);
+  }
+  return s;
+}
+}  // namespace contrib
+}  // namespace onnxruntime
diff --git a/onnxruntime/contrib_ops/cpu/tokenizer.h b/onnxruntime/contrib_ops/cpu/tokenizer.h
new file mode 100644
index 0000000000..0de73ca3fb
--- /dev/null
+++ b/onnxruntime/contrib_ops/cpu/tokenizer.h
@@ -0,0 +1,36 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#pragma once
+
+#include "core/framework/op_kernel.h"
+
+#include <memory>
+
+namespace onnxruntime {
+namespace contrib {
+class Tokenizer final : public OpKernel {
+ public:
+  explicit Tokenizer(const OpKernelInfo& info);
+  Tokenizer(const Tokenizer&) = delete;
+  Tokenizer& operator=(const Tokenizer&) = delete;
+  ~Tokenizer();
+
+  Status Compute(OpKernelContext* context) const override;
+
+ private:
+  Status CharTokenize(OpKernelContext* context, size_t N, size_t C,
+                      const std::vector<int64_t>& input_dims) const;
+
+  Status SeparatorTokenize(OpKernelContext* context, size_t N, size_t C,
+                           const std::vector<int64_t>& input_dims) const;
+
+  bool mark_;
+  std::string pad_value_;
+  int64_t mincharnum_;
+  bool char_tokenezation_;
+  struct SearchData;
+  std::unique_ptr<SearchData> search_data_;
+};
+}  // namespace contrib
+}  // namespace onnxruntime
diff --git a/onnxruntime/core/common/utf8_util.h b/onnxruntime/core/common/utf8_util.h
new file mode 100644
index 0000000000..bbc10bb094
--- /dev/null
+++ b/onnxruntime/core/common/utf8_util.h
@@ -0,0 +1,129 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#pragma once
+
+#include "core/common/common.h"
+
+namespace onnxruntime {
+namespace utf8_util {
+
+// Returns the number of bytes in the utf8 character
+// by analyzing its leading byte
+inline bool utf8_bytes(unsigned char ch, size_t& len) {
+  if ((ch & 0x80) == 0) {
+    len = 1;
+    return true;
+  }
+  if ((ch & 0xE0) == 0xC0) {
+    len = 2;
+    return true;
+  }
+  unsigned int result = (ch & 0xF0);
+  if (result == 0xE0) {
+    len = 3;
+    return true;
+  }
+  if (result == 0xF0) {
+    len = 4;
+    return true;
+  }
+  return false;
+}
+
+inline bool utf8_validate(const unsigned char* s, size_t len, size_t& utf8_chars) {
+  size_t utf8_len = 0;
+  size_t idx = 0;
+  while (idx < len) {
+    size_t bytes = 0;
+    auto ch = s[idx];
+    if (utf8_bytes(ch, bytes)) {
+      switch (bytes) {
+        case 1:
+          break;
+        case 2: {
+          if (++idx >= len || s[idx] < 0x80u || s[idx] > 0xBFu) {
+            return false;
+          }
+        } break;  // 2
+        case 3: {
+          auto ch1 = s[idx];
+          switch (ch1) {
+            case 0xE0u:
+              if (++idx >= len || s[idx] < 0xA0u || s[idx] > 0xBFu) {
+                return false;
+              }
+              break;
+            case 0xEDu:
+              if (++idx >= len || s[idx] < 0x80u || s[idx] > 0x9Fu) {
+                return false;
+              }
+              break;
+            default: {
+              if ((ch1 >= 0xE1u && ch1 <= 0xECu) ||
+                  (ch1 >= 0xEEu && ch1 <= 0xEFu)) {
+                if (++idx >= len || s[idx] < 0x80u || s[idx] > 0xBFu) {
+                  return false;
+                }
+              } else {
+                return false;
+              }
+            } break;
+          }
+          // validate byte 3
+          if (++idx >= len || s[idx] < 0x80u || s[idx] > 0xBFu) {
+            return false;
+          }
+        } break;  // 3
+        case 4: {
+          auto ch1 = s[idx];
+          switch (ch1) {
+            case 0xF0u: {
+              if (++idx >= len || s[idx] < 0x90u || s[idx] > 0xBFu) {
+                return false;
+              }
+            } break;
+            case 0xF4u: {
+              if (++idx >= len || s[idx] < 0x80u || s[idx] > 0x8Fu) {
+                return false;
+              }
+            } break;
+            default: {
+              if (ch1 >= 0xF1u && ch1 <= 0xF3u) {
+                if (++idx >= len || s[idx] < 0x80u || s[idx] > 0xBFu) {
+                  return false;
+                }
+              } else {
+                return false;
+              }
+            } break;
+          }
+          // validate bytes 3 and 4
+          size_t stop = idx + 2;
+          while (idx < stop) {
+            if (++idx >= len || s[idx] < 0x80u || s[idx] > 0xBFu) {
+              return false;
+            }
+          }
+        } break;  // 4
+        default:
+          // no chars longer than 4
+          return false;
+      }  // switch bytes
+      ++idx;
+      ++utf8_len;
+    } else {
+      return false;
+    }
+  }
+  // End index must match
+  // the end of the last byte sequence.
+  if (idx != len) {
+    return false;
+  }
+  utf8_chars = utf8_len;
+  return true;
+}
+
+}  // namespace utf8_util
+}  // namespace onnxruntime
diff --git a/onnxruntime/test/common/utf8_util_test.cc b/onnxruntime/test/common/utf8_util_test.cc
new file mode 100644
index 0000000000..47d631f977
--- /dev/null
+++ b/onnxruntime/test/common/utf8_util_test.cc
@@ -0,0 +1,46 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#include "core/common/utf8_util.h"
+#include "gtest/gtest.h"
+#include "test/providers/provider_test_utils.h"
+
+namespace onnxruntime {
+namespace test {
+
+struct Sample {
+  const char* sequence;
+  bool valid;
+};
+
+const std::vector<Sample> samples = {
+    {"a", true},
+    {"\xc3\xb1", true},
+    {"\xc3\x28", false},
+    {"\xa0\xa1", false},
+    {"\xe2\x82\xa1", true},
+    {"\xe2\x28\xa1", false},
+    {"\xe2\x82\x28", false},
+    {"\xf0\x90\x8c\xbc", true},
+    {"\xf0\x28\x8c\xbc", false},
+    {"\xf0\x90\x28\xbc", false},
+    {"\xf0\x28\x8c\x28", false},
+    {"\xf8\xa1\xa1\xa1\xa1", false},       // valid but not Unicode
+    {"\xfc\xa1\xa1\xa1\xa1\xa1", false}};  // valid but not Unicode
+
+TEST(Utf8UtilTest, Validate) {
+  using namespace utf8_util;
+  for (auto& s : samples) {
+    size_t utf8_len = 0;
+    if (s.valid != utf8_validate(reinterpret_cast<const unsigned char*>(s.sequence), strlen(s.sequence), utf8_len)) {
+      ASSERT_TRUE(false);
+    } else {
+      if (s.valid) {
+        ASSERT_EQ(1U, utf8_len);
+      }
+    }
+  }
+}
+
+}  // namespace test
+}  // namespace onnxruntime
diff --git a/onnxruntime/test/contrib_ops/tokenizer_test.cc b/onnxruntime/test/contrib_ops/tokenizer_test.cc
new file mode 100644
index 0000000000..2a22f90141
--- /dev/null
+++ b/onnxruntime/test/contrib_ops/tokenizer_test.cc
@@ -0,0 +1,708 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#include <codecvt>
+#include "gtest/gtest.h"
+#include "test/providers/provider_test_utils.h"
+
+namespace onnxruntime {
+namespace test {
+
+namespace tokenizer_test {
+const std::string start_mark{0x2};
+const std::string end_mark{0x3};
+const std::string padval("0xdeadbeaf");
+
+constexpr const char* domain = onnxruntime::kMSDomain;
+const int opset_ver = 1;
+
+}  // namespace tokenizer_test
+
+using namespace tokenizer_test;
+
+void InitTestAttr(OpTester& test, bool mark, const std::vector<std::string>& seps,
+                  int64_t mincharnum) {
+  test.AddAttribute("mark", int64_t{mark});
+  test.AddAttribute("separators", seps);
+  // Padding for alignment
+  test.AddAttribute("pad_value", padval);
+  test.AddAttribute("mincharnum", mincharnum);
+}
+
+TEST(ContribOpTest, TokenizerCharLevel_InvalidDim) {
+  // Invalid input dimensions
+  {
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, false, {""}, 1);
+
+    std::vector<int64_t> dims{1, 1, 2};
+    std::vector<std::string> input = {std::string("s1"), std::string("s2")};
+    test.AddInput<std::string>("T", dims, input);
+    std::vector<std::string> output(input);  // do the same for now
+    test.AddOutput<std::string>("Y", dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectFailure, "Input dimensions are either [C] or [N][C] allowed");
+  }
+}
+
+TEST(ContribOpTest, TokenizerCharLevel_LatinCharsNoMarkersC) {
+  // Char level tokenezation with latin characters and no
+  // start/end text markers
+  // [C] dimensions
+  // Output [C][D]
+  {
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, false, {""}, 1);
+
+    std::vector<int64_t> dims{2};
+    std::vector<std::string> input{"abcdef", "abcd"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    output_dims.push_back(int64_t(input[0].length()));
+    std::vector<std::string> output{
+        "a",
+        "b",
+        "c",
+        "d",
+        "e",
+        "f",
+        "a",
+        "b",
+        "c",
+        "d",
+        padval,
+        padval};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerCharLevel_LatinCharsWithMarkersC) {
+  // Char level tokenezation with latin characters and
+  // with start/end text markers
+  // [C] dimensions
+  // Output [C][D]
+  {
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, {""}, 1);
+
+    std::vector<int64_t> dims{2};
+    std::vector<std::string> input{"abcdef", "abcd"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    output_dims.push_back(int64_t(input[0].length() + 2));
+    std::vector<std::string> output{
+        start_mark,
+        "a",
+        "b",
+        "c",
+        "d",
+        "e",
+        "f",
+        end_mark,
+        start_mark,
+        "a",
+        "b",
+        "c",
+        "d",
+        end_mark,
+        padval,
+        padval};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerCharLevel_LatinCharsNoMarkersNC) {
+  // Char level tokenezation with latin characters and no
+  // start/end text markers
+  // [N][C] dimensions
+  // Output [N][C][D]
+  {
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, false, {""}, 1);
+
+    std::vector<int64_t> dims{2, 2};
+    std::vector<std::string> input{"abcd", "abcd", "abcd", "abcdef"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    output_dims.push_back(int64_t(input[3].length()));
+    std::vector<std::string> output{
+        "a",
+        "b",
+        "c",
+        "d",
+        padval,
+        padval,
+        "a",
+        "b",
+        "c",
+        "d",
+        padval,
+        padval,
+        "a",
+        "b",
+        "c",
+        "d",
+        padval,
+        padval,
+        "a",
+        "b",
+        "c",
+        "d",
+        "e",
+        "f"};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerCharLevel_LatinCharsWithMarkersNC) {
+  // Char level tokenezation with latin characters and
+  // with start/end text markers
+  // [N][C] dimensions
+  // Output [N][C][D]
+  {
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, {""}, 1);
+
+    std::vector<int64_t> dims{2, 2};
+    std::vector<std::string> input{"abcd", "abcd", "abcd", "abcdef"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    output_dims.push_back(int64_t(input[3].length() + 2));
+    std::vector<std::string> output{
+        start_mark,
+        "a",
+        "b",
+        "c",
+        "d",
+        end_mark,
+        padval,
+        padval,
+        start_mark,
+        "a",
+        "b",
+        "c",
+        "d",
+        end_mark,
+        padval,
+        padval,
+        start_mark,
+        "a",
+        "b",
+        "c",
+        "d",
+        end_mark,
+        padval,
+        padval,
+        start_mark,
+        "a",
+        "b",
+        "c",
+        "d",
+        "e",
+        "f",
+        end_mark};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerCharLevel_CyrillicCharsWithMarkersC) {
+  // Char level tokenezation with Cyrillic characters and
+  // with start/end text markers
+  // [C] dimensions
+  // Output [C][D]
+  {
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, {""}, 1);
+
+    std::vector<int64_t> dims{2};
+    std::vector<std::string> input{u8"Абсурд", u8"Кома"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    // Word Absurd is 6 chars long so we must get 6 individual strings out of it
+    // which is the max plus start/end text markers
+    output_dims.push_back(int64_t(6 + 2));
+    std::vector<std::string> output{
+        start_mark,
+        u8"А", u8"б", u8"с", u8"у", u8"р", u8"д",
+        end_mark,
+        start_mark,
+        u8"К", u8"о", u8"м", u8"а",
+        end_mark,
+        padval,
+        padval};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerCharLevel_MixedCharsWithMarkersC) {
+  // Char level tokenezation with a mix of latin, Spanish, Cyrillic and Chinese
+  // characters and
+  // with start/end text markers
+  // [C] dimensions
+  // Output [C][D]
+  {
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, {""}, 1);
+
+    std::vector<int64_t> dims{2};
+    std::vector<std::string> input{u8"Абсу中文", u8"Коñó"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    // Word Absu?? is 6 chars long so we must get 6 individual strings out of it
+    // which is the max plus start/end text markers
+    output_dims.push_back(int64_t(6 + 2));
+    std::vector<std::string> output{
+        start_mark,
+        u8"А", u8"б", u8"с", u8"у", u8"中", u8"文",
+        end_mark,
+        start_mark,
+        u8"К", u8"о", u8"ñ", u8"ó",
+        end_mark,
+        padval,
+        padval};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerCharLevel_EmptyOutputC) {
+  // Special case where empty output is produced
+  // For [C] we expect [C][0] output
+  {
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, {""}, 1);
+
+    std::vector<int64_t> dims{2};
+    std::vector<std::string> input{u8"", u8""};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    output_dims.push_back(int64_t(0));
+    std::vector<std::string> output{};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerCharLevel_EmptyOutputNC) {
+  // Special case where empty output is produced
+  // For [N][C] we expect [N][C][0] output
+  {
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, {""}, 1);
+
+    std::vector<int64_t> dims{2, 2};
+    std::vector<std::string> input{u8"", u8"", u8"", u8""};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    output_dims.push_back(int64_t(0));
+    std::vector<std::string> output{};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerWithSeparators_MixCharsWithMarkersC) {
+  // Separators and strings with a mix of latin, Spanish, Cyrillic and Chinese
+  // characters and with start/end text markers
+  // [C] dimensions
+  // Output [C][D]
+  {
+    std::vector<std::string> separators = {
+        u8"у",
+        u8"ñ"};
+
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, separators, 1);
+
+    std::vector<int64_t> dims{2};
+    std::vector<std::string> input{u8"Абсу中文", u8"Коñó"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    // Must split both in 2
+    output_dims.push_back(int64_t(2 + 2));
+    std::vector<std::string> output{
+        start_mark,
+        u8"Абс", u8"中文",
+        end_mark,
+        start_mark,
+        u8"Ко", u8"ó",
+        end_mark};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }  // namespace test
+}
+
+TEST(ContribOpTest, TokenizerWithSeparators_MixCharsWithMarkersCompleteMatchEmptyOutputC) {
+  // Test entire separators match so we get nothing
+  // in the output
+  {
+    std::vector<std::string> separators = {
+        u8"Абсу中文",
+        u8"Коñó"};
+
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, separators, 1);
+
+    std::vector<int64_t> dims{2};
+    std::vector<std::string> input{u8"Абсу中文", u8"Коñó"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    // Must have no output
+    output_dims.push_back(int64_t(0));
+    std::vector<std::string> output;
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerWithSeparators_MixCharsWithMarkersStartMatchC) {
+  // Match the start
+  {
+    std::vector<std::string> separators = {
+        u8"А",
+        u8"К"};
+
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, separators, 1);
+
+    std::vector<int64_t> dims{2};
+    std::vector<std::string> input{u8"Абсу中文", u8"Коñó"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    // Must drop first characters from both strings
+    output_dims.push_back(int64_t(3));
+    std::vector<std::string> output{
+        start_mark,
+        u8"бсу中文",
+        end_mark,
+        start_mark,
+        u8"оñó",
+        end_mark};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerWithSeparators_MixCharsWithMarkersEndMatchC) {
+  // Match the end
+  {
+    std::vector<std::string> separators = {
+        u8"文",
+        u8"ó"};
+
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, separators, 1);
+
+    std::vector<int64_t> dims{2};
+    std::vector<std::string> input{u8"Абсу中文", u8"Коñó"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    // Must drop last characters from both strings
+    output_dims.push_back(int64_t(3));
+    std::vector<std::string> output{
+        start_mark,
+        u8"Абсу中",
+        end_mark,
+        start_mark,
+        u8"Коñ",
+        end_mark};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerWithSeparators_MixCharsWithMarkersEndMatchAtLeast4CharsC) {
+  // Match the end, require at least 4 chars
+  {
+    std::vector<std::string> separators = {
+        u8"文",
+        u8"ó"};
+
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, separators, 4);
+
+    std::vector<int64_t> dims{2};
+    std::vector<std::string> input{u8"Абсу中文", u8"Коñó"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    // Must drop the last character from the first
+    // and the second 3 character token does not pass mincharnum
+    output_dims.push_back(int64_t(3));
+    std::vector<std::string> output{
+        start_mark,
+        u8"Абсу中",
+        end_mark,
+        start_mark,
+        end_mark,
+        padval};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerWithSeparators_MixCharsWithMarkersEmptyInputEmptyOutputC) {
+  // Empty input for [C] should produce [C][0]
+  {
+    std::vector<std::string> separators = {
+        u8"文",
+        u8"ó"};
+
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, separators, 4);
+
+    std::vector<int64_t> dims{2};
+    std::vector<std::string> input{u8"", u8""};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    output_dims.push_back(int64_t(0));
+    std::vector<std::string> output;
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerWithSeparators_MixCharsWithMarkersEmptyInputEmptyOutputNC) {
+  // Empty input for [N][C] should produce [N][C][0]
+  {
+    std::vector<std::string> separators = {
+        u8"文",
+        u8"ó"};
+
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, true, separators, 4);
+
+    std::vector<int64_t> dims{2, 2};
+    std::vector<std::string> input{u8"", u8"文", u8"ó", u8""};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    output_dims.push_back(int64_t(0));
+    std::vector<std::string> output;
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerWithSeparators_MixCharsNoMarkersSeparatorsOverlapShortFirstC) {
+  // Test of the overlapping search patterns
+  // The spec mandates that the patterns that appear
+  // in the separators earlier must be matched first.
+  {
+    // In this case the first pattern must match first
+    // and there would be no match for the second
+    std::vector<std::string> separators = {
+        u8"су",
+        u8"Абсу"};
+
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, false, separators, 1);
+
+    std::vector<int64_t> dims{1};
+    std::vector<std::string> input{u8"Абсу中文"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    // must split in 2 with no two middle characters
+    output_dims.push_back(int64_t(2));
+    std::vector<std::string> output{
+        u8"Аб", u8"中文"};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerWithSeparators_MixCharsNoMarkersSeparatorsOverlapLongFirstC) {
+  // Test of the overlapping search patterns
+  // The spec mandates that the patterns that appear
+  // in the separators earlier must be matched first.
+  {
+    // In this case the first pattern must match first
+    // and there would be no match for the second
+    std::vector<std::string> separators = {
+        u8"Абсу",
+        u8"су"};
+
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, false, separators, 1);
+
+    std::vector<int64_t> dims{1};
+    std::vector<std::string> input{u8"Абсу中文"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    // Must drop the beginning of the word that
+    // also contains the second separator
+    output_dims.push_back(int64_t(1));
+    std::vector<std::string> output{u8"中文"};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerWithSeparators_MixCharsNoMarkersSeparatorsOverlapLongFirstRepeatedShortC) {
+  // Test of the overlapping search patterns
+  // The spec mandates that the patterns that appear
+  // in the separators earlier must be matched first.
+  {
+    // In this case the first pattern must match first
+    // and there would be no match for the second
+    std::vector<std::string> separators = {
+        u8"Абсу",
+        u8"су"};
+
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, false, separators, 1);
+
+    std::vector<int64_t> dims{1};
+    std::vector<std::string> input{u8"Абсусусу中文"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    // Must drop the beginning of the word that
+    // also contains the second separator
+    output_dims.push_back(int64_t(1));
+    std::vector<std::string> output{u8"中文"};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerWithSeparators_MixCharsNoMarkersSeparatorsOverlapingMatchC) {
+  // Test of the overlapping search patterns
+  // The spec mandates that the patterns that appear
+  // in the separators earlier must be matched first.
+  {
+    // In this case the first pattern must match first
+    // and there are more than one overlapping matches for the first
+    // so the earlier match for the first wins.
+    // and there would be no match for the second
+    std::vector<std::string> separators = {
+        u8"усу",
+        u8"Абсу"};
+
+    OpTester test("Tokenizer", opset_ver, domain);
+    InitTestAttr(test, false, separators, 1);
+
+    std::vector<int64_t> dims{1};
+    std::vector<std::string> input{u8"Абсусусу中文"};
+    test.AddInput<std::string>("T", dims, input);
+
+    std::vector<int64_t> output_dims(dims);
+    // Must drop the beginning of the word that
+    // also contains the second separator
+    output_dims.push_back(int64_t(2));
+    std::vector<std::string> output{u8"Абс", u8"су中文"};
+
+    test.AddOutput<std::string>("Y", output_dims, output);
+
+    test.Run(OpTester::ExpectResult::kExpectSuccess);
+  }
+}
+
+TEST(ContribOpTest, TokenizerWithSeparators_MixCharCommonPrefixC) {
+  // Separators and strings with a mix of latin, Spanish, Cyrillic and Chinese
+  // characters and with start/end text markers
+  // [C] dimensions
+  // Output [C][D]
+  std::vector<std::string> separators = {
+      u8";",
+      u8";;;"};
+
+  OpTester test("Tokenizer", opset_ver, domain);
+  InitTestAttr(test, true, separators, 1);
+
+  std::vector<int64_t> dims{4};
+  std::vector<std::string> input{u8"a;b", u8"a;;;b", u8"b;c;;;d;e", u8"a;;b;;;c"};
+  test.AddInput<std::string>("T", dims, input);
+
+  std::vector<int64_t> output_dims(dims);
+  // Must split both in 2
+  output_dims.push_back(int64_t(6));
+  std::vector<std::string> output{
+      start_mark,
+      u8"a",
+      u8"b",
+      end_mark,
+      padval,
+      padval,
+      start_mark,
+      u8"a",
+      u8"b",
+      end_mark,
+      padval,
+      padval,
+      start_mark,
+      u8"b",
+      u8"c",
+      u8"d",
+      u8"e",
+      end_mark,
+      start_mark,
+      u8"a",
+      u8"b",
+      u8"c",
+      end_mark,
+      padval,
+  };
+
+  test.AddOutput<std::string>("Y", output_dims, output);
+  test.Run(OpTester::ExpectResult::kExpectSuccess);
+}
+
+}  // namespace test
+}  // namespace onnxruntime