diff --git a/Firestore/CHANGELOG.md b/Firestore/CHANGELOG.md
index 6a4973c7b02..5ee300f8015 100644
--- a/Firestore/CHANGELOG.md
+++ b/Firestore/CHANGELOG.md
@@ -1,3 +1,7 @@
+# Unreleased
+- [fixed] Marked all public classes with only readonly properties as `Sendable` to address
+  Swift Concurrency Check warning. (#12666)
+
 # 11.1.0
 - [feature] Add `VectorValue` type support.
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRAggregateField.h b/Firestore/Source/Public/FirebaseFirestore/FIRAggregateField.h
index be7826489a3..36706d6c165 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRAggregateField.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRAggregateField.h
@@ -23,6 +23,7 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  * Represents an aggregation that can be performed by Firestore.
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(AggregateField)
 @interface FIRAggregateField : NSObject
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRAggregateQuery.h b/Firestore/Source/Public/FirebaseFirestore/FIRAggregateQuery.h
index 8170d5caa53..764d395f728 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRAggregateQuery.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRAggregateQuery.h
@@ -26,6 +26,7 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  * A query that calculates aggregations over an underlying query.
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(AggregateQuery)
 @interface FIRAggregateQuery : NSObject
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRAggregateQuerySnapshot.h b/Firestore/Source/Public/FirebaseFirestore/FIRAggregateQuerySnapshot.h
index 9a558bebed2..220a09cef17 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRAggregateQuerySnapshot.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRAggregateQuerySnapshot.h
@@ -24,6 +24,7 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  * The results of executing an `AggregateQuery`.
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(AggregateQuerySnapshot)
 @interface FIRAggregateQuerySnapshot : NSObject
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRCollectionReference.h b/Firestore/Source/Public/FirebaseFirestore/FIRCollectionReference.h
index 40ece263952..e0ad130531b 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRCollectionReference.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRCollectionReference.h
@@ -26,6 +26,7 @@ NS_ASSUME_NONNULL_BEGIN
  * A `CollectionReference` object can be used for adding documents, getting document references,
  * and querying for documents (using the methods inherited from `Query`).
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(CollectionReference)
 @interface FIRCollectionReference : FIRQuery
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRDocumentChange.h b/Firestore/Source/Public/FirebaseFirestore/FIRDocumentChange.h
index e36f77382e4..c33166f4043 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRDocumentChange.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRDocumentChange.h
@@ -43,6 +43,7 @@ typedef NS_ENUM(NSInteger, FIRDocumentChangeType)
  * A `DocumentChange` represents a change to the documents matching a query. It contains the
  * document affected and the type of change that occurred (added, modified, or removed).
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(DocumentChange)
 @interface FIRDocumentChange : NSObject
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRDocumentReference.h b/Firestore/Source/Public/FirebaseFirestore/FIRDocumentReference.h
index b6f87450cb3..e340057db22 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRDocumentReference.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRDocumentReference.h
@@ -39,6 +39,7 @@ typedef void (^FIRDocumentSnapshotBlock)(FIRDocumentSnapshot *_Nullable snapshot
  * may or may not exist. A `DocumentReference` can also be used to create a `CollectionReference` to
  * a subcollection.
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(DocumentReference)
 @interface FIRDocumentReference : NSObject
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRDocumentSnapshot.h b/Firestore/Source/Public/FirebaseFirestore/FIRDocumentSnapshot.h
index ef6e011863e..72a699879eb 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRDocumentSnapshot.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRDocumentSnapshot.h
@@ -55,6 +55,7 @@ typedef NS_ENUM(NSInteger, FIRServerTimestampBehavior) {
  * For a `DocumentSnapshot` that points to a non-existing document, any data access will return
  * `nil`. You can use the `exists` property to explicitly verify a documents existence.
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(DocumentSnapshot)
 @interface FIRDocumentSnapshot : NSObject
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRFieldPath.h b/Firestore/Source/Public/FirebaseFirestore/FIRFieldPath.h
index 9f64fbdc99d..e64bd4e95a0 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRFieldPath.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRFieldPath.h
@@ -23,6 +23,7 @@ NS_ASSUME_NONNULL_BEGIN
  * (referring to a top level field in the document), or a list of field names (referring to a nested
  * field in the document).
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(FieldPath)
 @interface FIRFieldPath : NSObject <NSCopying>
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRFieldValue.h b/Firestore/Source/Public/FirebaseFirestore/FIRFieldValue.h
index 8add3dec1fa..9defa3a0569 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRFieldValue.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRFieldValue.h
@@ -22,6 +22,7 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  * Sentinel values that can be used when writing document fields with `setData()` or `updateData()`.
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(FieldValue)
 @interface FIRFieldValue : NSObject
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRFilter.h b/Firestore/Source/Public/FirebaseFirestore/FIRFilter.h
index ef5946eda63..788ecda2554 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRFilter.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRFilter.h
@@ -24,6 +24,7 @@ NS_ASSUME_NONNULL_BEGIN
  * A Filter represents a restriction on one or more field values and can be used to refine
  * the results of a Query.
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(Filter)
 @interface FIRFilter : NSObject
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRGeoPoint.h b/Firestore/Source/Public/FirebaseFirestore/FIRGeoPoint.h
index 4454225caf8..05d864f8475 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRGeoPoint.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRGeoPoint.h
@@ -25,6 +25,7 @@ NS_ASSUME_NONNULL_BEGIN
  * Latitude values are in the range of [-90, 90].
  * Longitude values are in the range of [-180, 180].
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(GeoPoint)
 @interface FIRGeoPoint : NSObject <NSCopying>
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRLoadBundleTask.h b/Firestore/Source/Public/FirebaseFirestore/FIRLoadBundleTask.h
index ff237f3a19a..aa241895d7f 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRLoadBundleTask.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRLoadBundleTask.h
@@ -36,6 +36,7 @@ typedef NS_ENUM(NSInteger, FIRLoadBundleTaskState) {
 
 /** Represents a progress update or a final state from loading bundles. */
 NS_SWIFT_NAME(LoadBundleTaskProgress)
+NS_SWIFT_SENDABLE
 @interface FIRLoadBundleTaskProgress : NSObject
 
 /** How many documents have been loaded. */
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRQuery.h b/Firestore/Source/Public/FirebaseFirestore/FIRQuery.h
index c75952876a2..dad8bbd1eed 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRQuery.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRQuery.h
@@ -41,6 +41,7 @@ typedef void (^FIRQuerySnapshotBlock)(FIRQuerySnapshot *_Nullable snapshot,
  * A `Query` refers to a query which you can read or listen to. You can also construct
  * refined `Query` objects by adding filters and ordering.
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(Query)
 @interface FIRQuery : NSObject
 /** :nodoc: */
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRQuerySnapshot.h b/Firestore/Source/Public/FirebaseFirestore/FIRQuerySnapshot.h
index f3e80b94564..8c649755a35 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRQuerySnapshot.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRQuerySnapshot.h
@@ -28,6 +28,7 @@ NS_ASSUME_NONNULL_BEGIN
  * using the `documents` property and its size can be inspected with `isEmpty` and
  * `count`.
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(QuerySnapshot)
 @interface FIRQuerySnapshot : NSObject
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRSnapshotListenOptions.h b/Firestore/Source/Public/FirebaseFirestore/FIRSnapshotListenOptions.h
index c1ef6a3a3a1..b866a114212 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRSnapshotListenOptions.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRSnapshotListenOptions.h
@@ -44,6 +44,7 @@ typedef NS_ENUM(NSUInteger, FIRListenSource) {
  * of this class control settings like whether metadata-only changes trigger events and the
  * preferred data source.
  */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(SnapshotListenOptions)
 @interface FIRSnapshotListenOptions : NSObject
 
diff --git a/Firestore/Source/Public/FirebaseFirestore/FIRSnapshotMetadata.h b/Firestore/Source/Public/FirebaseFirestore/FIRSnapshotMetadata.h
index 04e19c1ba68..ad26df21af2 100644
--- a/Firestore/Source/Public/FirebaseFirestore/FIRSnapshotMetadata.h
+++ b/Firestore/Source/Public/FirebaseFirestore/FIRSnapshotMetadata.h
@@ -19,6 +19,7 @@
 NS_ASSUME_NONNULL_BEGIN
 
 /** Metadata about a snapshot, describing the state of the snapshot. */
+NS_SWIFT_SENDABLE
 NS_SWIFT_NAME(SnapshotMetadata)
 @interface FIRSnapshotMetadata : NSObject
 
diff --git a/Firestore/Swift/Tests/API/BasicCompileTests.swift b/Firestore/Swift/Tests/API/BasicCompileTests.swift
index 480f85be3a1..01d2678ff09 100644
--- a/Firestore/Swift/Tests/API/BasicCompileTests.swift
+++ b/Firestore/Swift/Tests/API/BasicCompileTests.swift
@@ -493,36 +493,40 @@ func terminateDb(database db: Firestore) {
   }
 }
 
-#if swift(>=5.5.2)
-  @available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
-  func testAsyncAwait(database db: Firestore) async throws {
-    try await db.enableNetwork()
-    try await db.disableNetwork()
-    try await db.waitForPendingWrites()
-    try await db.clearPersistence()
-    try await db.terminate()
-    try await db.runTransaction { _, _ in
-      0
-    }
+@available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
+func testAsyncAwait(database db: Firestore) async throws {
+  try await db.enableNetwork()
+  try await db.disableNetwork()
+  try await db.waitForPendingWrites()
+  try await db.clearPersistence()
+  try await db.terminate()
+  _ = try await db.runTransaction { _, _ in
+    0
+  }
 
-    let batch = db.batch()
-    try await batch.commit()
+  let batch = db.batch()
+  try await batch.commit()
 
-    _ = await db.getQuery(named: "foo")
-    _ = try await db.loadBundle(Data())
+  _ = await db.getQuery(named: "foo")
+  _ = try await db.loadBundle(Data())
 
-    let collection = db.collection("coll")
-    try await collection.getDocuments()
-    try await collection.getDocuments(source: FirestoreSource.default)
+  let collection = db.collection("coll")
+  try await collection.getDocuments()
+  try await collection.getDocuments(source: FirestoreSource.default)
 
-    let document = try await collection.addDocument(data: [:])
+  let document = try await collection.addDocument(data: [:])
 
-    try await document.setData([:])
-    try await document.setData([:], merge: true)
-    try await document.setData([:], mergeFields: [])
-    try await document.updateData([:])
-    try await document.delete()
-    try await document.getDocument()
-    try await document.getDocument(source: FirestoreSource.default)
+  try await document.setData([:])
+  try await document.setData([:], merge: true)
+  try await document.setData([:], mergeFields: [])
+  try await document.updateData([:])
+  try await document.delete()
+  try await document.getDocument()
+  try await document.getDocument(source: FirestoreSource.default)
+}
+
+actor regression12666 {
+  func getUser() async throws {
+    _ = try await Firestore.firestore().collection("users").getDocuments()
   }
-#endif
+}