diff --git a/.librarian/generator-input/client-post-processing/firestore-integration.yaml b/.librarian/generator-input/client-post-processing/firestore-integration.yaml
index 429d658d8e96..49fd20d5f427 100644
--- a/.librarian/generator-input/client-post-processing/firestore-integration.yaml
+++ b/.librarian/generator-input/client-post-processing/firestore-integration.yaml
@@ -75,6 +75,7 @@ replacements:
           BSONMaxKey,
           BSONMinKey,
           BSONObjectId,
+          BSONRegex,
           BSONTimestamp,
       )
       from google.cloud.firestore_v1.client import Client
@@ -183,6 +184,7 @@ replacements:
           "BSONMaxKey",
           "BSONMinKey",
           "BSONObjectId",
+          "BSONRegex",
           "BSONTimestamp",
           "Client",
           "CountAggregation",
@@ -261,6 +263,7 @@ replacements:
           BSONMaxKey,
           BSONMinKey,
           BSONObjectId,
+          BSONRegex,
           BSONTimestamp,
           Client,
           CollectionGroup,
@@ -324,6 +327,7 @@ replacements:
           "BSONMaxKey",
           "BSONMinKey",
           "BSONObjectId",
+          "BSONRegex",
           "BSONTimestamp",
           "Client",
           "CountAggregation",
diff --git a/packages/google-cloud-firestore/google/cloud/firestore/__init__.py b/packages/google-cloud-firestore/google/cloud/firestore/__init__.py
index e89628a94ac1..eaa2daacd0f1 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore/__init__.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore/__init__.py
@@ -40,6 +40,7 @@
     BSONMaxKey,
     BSONMinKey,
     BSONObjectId,
+    BSONRegex,
     BSONTimestamp,
     Client,
     CollectionGroup,
@@ -103,6 +104,7 @@
     "BSONMaxKey",
     "BSONMinKey",
     "BSONObjectId",
+    "BSONRegex",
     "BSONTimestamp",
     "Client",
     "CountAggregation",
diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/__init__.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/__init__.py
index 9d629e864507..e7445eeedf3a 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/__init__.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/__init__.py
@@ -52,6 +52,7 @@
     BSONMaxKey,
     BSONMinKey,
     BSONObjectId,
+    BSONRegex,
     BSONTimestamp,
 )
 from google.cloud.firestore_v1.client import Client
@@ -160,6 +161,7 @@
     "BSONMaxKey",
     "BSONMinKey",
     "BSONObjectId",
+    "BSONRegex",
     "BSONTimestamp",
     "Client",
     "CountAggregation",
diff --git a/packages/google-cloud-firestore/google/cloud/firestore_v1/bson.py b/packages/google-cloud-firestore/google/cloud/firestore_v1/bson.py
index fecf9d2aea7c..40b7ef346566 100644
--- a/packages/google-cloud-firestore/google/cloud/firestore_v1/bson.py
+++ b/packages/google-cloud-firestore/google/cloud/firestore_v1/bson.py
@@ -35,6 +35,7 @@
     "BSONInt32",
     "BSONBinary",
     "BSONTimestamp",
+    "BSONRegex",
 ]
 
 _OBJECT_ID_BYTES_LEN = 12
@@ -342,3 +343,85 @@ def __eq__(self, other: Any) -> bool:
 
     def __hash__(self) -> int:
         return hash((type(self), self._seconds, self._increment))
+
+
+class BSONRegex(_BSONType):
+    """Represents a BSON Regular Expression container for Firestore.
+
+    Args:
+        pattern (str): The regular expression pattern string.
+        options (Union[str, re.RegexFlag, int], optional): BSON regex option flags
+            as a string (e.g. "i", "m", "s") or Python `re` flag integer (e.g. `re.I | re.M`).
+            Defaults to "".
+
+    Raises:
+        TypeError: If pattern is not a string or options is invalid type.
+
+    Example:
+        >>> regex = BSONRegex("^hello.*$", options="i")
+        >>> regex.pattern
+        '^hello.*$'
+        >>> regex.options
+        'i'
+    """
+
+    __slots__ = ("_pattern", "_options")
+
+    _FLAG_TO_OPTION: Dict[int, str] = {
+        re.IGNORECASE: "i",
+        re.LOCALE: "l",
+        re.MULTILINE: "m",
+        re.DOTALL: "s",
+        re.UNICODE: "u",
+        re.VERBOSE: "x",
+    }
+
+    def __init__(self, pattern: str, options: Union[str, re.RegexFlag, int] = ""):
+        if not isinstance(pattern, str):
+            raise TypeError("BSONRegex pattern must be a str.")
+
+        if isinstance(options, bool):
+            raise TypeError("BSONRegex options must be a str or re flag integer.")
+
+        if isinstance(options, str):
+            self._options: str = "".join(sorted(set(options)))
+        elif isinstance(options, int):
+            opts = []
+            for flag, char in self._FLAG_TO_OPTION.items():
+                if options & flag:
+                    opts.append(char)
+            self._options = "".join(sorted(opts))
+        else:
+            raise TypeError("BSONRegex options must be a str or re flag integer.")
+
+        self._pattern: str = pattern
+
+    @property
+    def pattern(self) -> str:
+        """str: The regular expression pattern string."""
+        return self._pattern
+
+    @property
+    def options(self) -> str:
+        """str: The normalized BSON regex option flags sorted alphabetically."""
+        return self._options
+
+    def _to_map_value(self) -> Dict[str, Dict[str, str]]:
+        """Returns map dictionary representation for wire serialization."""
+        return {
+            "__regex__": {
+                "pattern": self._pattern,
+                "options": self._options,
+            }
+        }
+
+    def __repr__(self) -> str:
+        return f"BSONRegex({self._pattern!r}, options={self._options!r})"
+
+    def __eq__(self, other: Any) -> bool:
+        if isinstance(other, BSONRegex):
+            return self._pattern == other._pattern and self._options == other._options
+        return NotImplemented
+
+    def __hash__(self) -> int:
+        return hash((type(self), self._pattern, self._options))
diff --git a/packages/google-cloud-firestore/tests/system/test_system.py b/packages/google-cloud-firestore/tests/system/test_system.py
index 7997c95265b3..bee648ace9b3 100644
--- a/packages/google-cloud-firestore/tests/system/test_system.py
+++ b/packages/google-cloud-firestore/tests/system/test_system.py
@@ -54,6 +54,7 @@
     BSONMaxKey,
     BSONMinKey,
     BSONObjectId,
+    BSONRegex,
     BSONTimestamp,
 )
 from google.cloud.firestore_v1.vector import Vector
@@ -1296,6 +1297,7 @@ def test_bson_document_writes(client, cleanup, database):
         "int32_val": BSONInt32(42),
         "binary_val_sub128": BSONBinary(b"world", subtype=128),
         "timestamp_val": BSONTimestamp(1700000000, 1),
+        "regex_val": BSONRegex("^hello.*$", options="i"),
     }
 
     doc_ref.set(bson_payload)
@@ -1314,6 +1316,12 @@ def test_bson_document_writes(client, cleanup, database):
                 "increment": 1,
             }
         },
+        "regex_val": {
+            "__regex__": {
+                "pattern": "^hello.*$",
+                "options": "i",
+            }
+        },
     }
 
 
diff --git a/packages/google-cloud-firestore/tests/system/test_system_async.py b/packages/google-cloud-firestore/tests/system/test_system_async.py
index 24ebf2992ea0..479fa66ee860 100644
--- a/packages/google-cloud-firestore/tests/system/test_system_async.py
+++ b/packages/google-cloud-firestore/tests/system/test_system_async.py
@@ -57,6 +57,7 @@
     BSONMaxKey,
     BSONMinKey,
     BSONObjectId,
+    BSONRegex,
     BSONTimestamp,
 )
 from google.cloud.firestore_v1.query_profile import (
@@ -1269,6 +1270,7 @@ async def test_async_bson_document_writes(client, cleanup, database):
         "int32_val": BSONInt32(42),
         "binary_val_sub128": BSONBinary(b"world", subtype=128),
         "timestamp_val": BSONTimestamp(1700000000, 1),
+        "regex_val": BSONRegex("^hello.*$", options="i"),
     }
 
     await doc_ref.set(bson_payload)
@@ -1287,6 +1289,12 @@ async def test_async_bson_document_writes(client, cleanup, database):
                 "increment": 1,
             }
         },
+        "regex_val": {
+            "__regex__": {
+                "pattern": "^hello.*$",
+                "options": "i",
+            }
+        },
     }
 
 
diff --git a/packages/google-cloud-firestore/tests/unit/v1/test_bson.py b/packages/google-cloud-firestore/tests/unit/v1/test_bson.py
index d90328d4cc1c..b5be269f0061 100644
--- a/packages/google-cloud-firestore/tests/unit/v1/test_bson.py
+++ b/packages/google-cloud-firestore/tests/unit/v1/test_bson.py
@@ -17,6 +17,7 @@
 
 import copy
 import pickle
+import re
 
 import pytest
 
@@ -26,6 +27,7 @@
     BSONMaxKey,
     BSONMinKey,
     BSONObjectId,
+    BSONRegex,
     BSONTimestamp,
     _BSONType,
 )
@@ -411,3 +413,72 @@ def test_bson_timestamp_copy():
 def test_bson_timestamp_pickle():
     ts = BSONTimestamp(100, 1)
     assert pickle.loads(pickle.dumps(ts)) == ts
+
+
+def test_bson_regex_valid():
+    rx = BSONRegex("^hello.*$", options="i")
+    assert rx.pattern == "^hello.*$"
+    assert rx.options == "i"
+    assert rx._to_map_value() == {
+        "__regex__": {
+            "pattern": "^hello.*$",
+            "options": "i",
+        }
+    }
+    assert repr(rx) == "BSONRegex('^hello.*$', options='i')"
+
+
+def test_bson_regex_options_sorting_and_deduplication():
+    rx1 = BSONRegex("foo", options="msi")
+    assert rx1.options == "ims"
+
+    rx2 = BSONRegex("foo", options="mmiis")
+    assert rx2.options == "ims"
+
+
+def test_bson_regex_options_from_re_flags():
+    rx = BSONRegex("foo", options=re.IGNORECASE | re.MULTILINE)
+    assert rx.options == "im"
+
+
+@pytest.mark.parametrize(
+    "pattern_input, options_input, exc_type, match_msg",
+    [
+        (123, "i", TypeError, "pattern must be a str"),
+        (None, "i", TypeError, "pattern must be a str"),
+        ("foo", True, TypeError, "options must be a str or re flag integer"),
+        ("foo", [1, 2], TypeError, "options must be a str or re flag integer"),
+    ],
+)
+def test_bson_regex_invalid_inputs(pattern_input, options_input, exc_type, match_msg):
+    with pytest.raises(exc_type, match=match_msg):
+        BSONRegex(pattern_input, options_input)
+
+
+def test_bson_regex_equality():
+    rx1 = BSONRegex("^abc", options="i")
+    rx2 = BSONRegex("^abc", options="i")
+    rx3 = BSONRegex("^abc", options="m")
+    rx4 = BSONRegex("^xyz", options="i")
+    assert rx1 == rx2
+    assert rx1 != rx3
+    assert rx1 != rx4
+    assert rx1 != "^abc"
+
+
+def test_bson_regex_hash_and_dict_key():
+    rx1 = BSONRegex("^abc", options="i")
+    rx2 = BSONRegex("^abc", options="i")
+    assert hash(rx1) == hash(rx2)
+    assert len({rx1, rx2}) == 1
+
+
+def test_bson_regex_copy():
+    rx = BSONRegex("^abc", options="i")
+    assert copy.copy(rx) == rx
+    assert copy.deepcopy(rx) == rx
+
+
+def test_bson_regex_pickle():
+    rx = BSONRegex("^abc", options="i")
+    assert pickle.loads(pickle.dumps(rx)) == rx