diff --git a/firebase-firestore/CHANGELOG.md b/firebase-firestore/CHANGELOG.md
index 29416bcf9a4..a02bc7efccf 100644
--- a/firebase-firestore/CHANGELOG.md
+++ b/firebase-firestore/CHANGELOG.md
@@ -1,5 +1,5 @@
 # Unreleased
-
+* [fixed] Remove copy of Guava Function interface, and instead use Guava directly. [#6983](//github.com/firebase/firebase-android-sdk/pull/6983)
 
 # 25.1.4
 * [fixed] Fixed the `null` value handling in `whereNotEqualTo` and `whereNotIn` filters.
diff --git a/firebase-firestore/src/androidTest/java/com/google/firebase/firestore/AccessHelper.java b/firebase-firestore/src/androidTest/java/com/google/firebase/firestore/AccessHelper.java
index d0800b5ce4a..4a44b32738e 100644
--- a/firebase-firestore/src/androidTest/java/com/google/firebase/firestore/AccessHelper.java
+++ b/firebase-firestore/src/androidTest/java/com/google/firebase/firestore/AccessHelper.java
@@ -15,13 +15,13 @@
 package com.google.firebase.firestore;
 
 import android.content.Context;
+import com.google.common.base.Function;
 import com.google.firebase.FirebaseApp;
 import com.google.firebase.firestore.auth.CredentialsProvider;
 import com.google.firebase.firestore.auth.User;
 import com.google.firebase.firestore.core.ComponentProvider;
 import com.google.firebase.firestore.model.DatabaseId;
 import com.google.firebase.firestore.util.AsyncQueue;
-import com.google.firebase.firestore.util.Function;
 
 /** Gives access to package private methods in integration tests. */
 public final class AccessHelper {
diff --git a/firebase-firestore/src/main/java/com/google/firebase/firestore/FirebaseFirestore.java b/firebase-firestore/src/main/java/com/google/firebase/firestore/FirebaseFirestore.java
index c1218829b8a..aef1f2c0347 100644
--- a/firebase-firestore/src/main/java/com/google/firebase/firestore/FirebaseFirestore.java
+++ b/firebase-firestore/src/main/java/com/google/firebase/firestore/FirebaseFirestore.java
@@ -27,6 +27,7 @@
 import com.google.android.gms.tasks.Task;
 import com.google.android.gms.tasks.TaskCompletionSource;
 import com.google.android.gms.tasks.Tasks;
+import com.google.common.base.Function;
 import com.google.firebase.FirebaseApp;
 import com.google.firebase.annotations.PreviewApi;
 import com.google.firebase.appcheck.interop.InteropAppCheckTokenProvider;
@@ -51,7 +52,6 @@
 import com.google.firebase.firestore.util.AsyncQueue;
 import com.google.firebase.firestore.util.ByteBufferInputStream;
 import com.google.firebase.firestore.util.Executors;
-import com.google.firebase.firestore.util.Function;
 import com.google.firebase.firestore.util.Logger;
 import com.google.firebase.firestore.util.Logger.Level;
 import com.google.firebase.firestore.util.Preconditions;
diff --git a/firebase-firestore/src/main/java/com/google/firebase/firestore/FirestoreClientProvider.java b/firebase-firestore/src/main/java/com/google/firebase/firestore/FirestoreClientProvider.java
index bebd57e3160..5b87aafdc09 100644
--- a/firebase-firestore/src/main/java/com/google/firebase/firestore/FirestoreClientProvider.java
+++ b/firebase-firestore/src/main/java/com/google/firebase/firestore/FirestoreClientProvider.java
@@ -18,9 +18,9 @@
 import androidx.annotation.VisibleForTesting;
 import androidx.core.util.Consumer;
 import com.google.android.gms.tasks.Task;
+import com.google.common.base.Function;
 import com.google.firebase.firestore.core.FirestoreClient;
 import com.google.firebase.firestore.util.AsyncQueue;
-import com.google.firebase.firestore.util.Function;
 import java.util.concurrent.Executor;
 
 /**
diff --git a/firebase-firestore/src/main/java/com/google/firebase/firestore/core/CompositeFilter.java b/firebase-firestore/src/main/java/com/google/firebase/firestore/core/CompositeFilter.java
index 26654f7a1ba..33abfb5f1b4 100644
--- a/firebase-firestore/src/main/java/com/google/firebase/firestore/core/CompositeFilter.java
+++ b/firebase-firestore/src/main/java/com/google/firebase/firestore/core/CompositeFilter.java
@@ -16,8 +16,8 @@
 
 import android.text.TextUtils;
 import androidx.annotation.Nullable;
+import com.google.common.base.Function;
 import com.google.firebase.firestore.model.Document;
-import com.google.firebase.firestore.util.Function;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
diff --git a/firebase-firestore/src/main/java/com/google/firebase/firestore/core/FirestoreClient.java b/firebase-firestore/src/main/java/com/google/firebase/firestore/core/FirestoreClient.java
index 6e2d9b87b84..b9feb43e515 100644
--- a/firebase-firestore/src/main/java/com/google/firebase/firestore/core/FirestoreClient.java
+++ b/firebase-firestore/src/main/java/com/google/firebase/firestore/core/FirestoreClient.java
@@ -22,6 +22,7 @@
 import com.google.android.gms.tasks.Task;
 import com.google.android.gms.tasks.TaskCompletionSource;
 import com.google.android.gms.tasks.Tasks;
+import com.google.common.base.Function;
 import com.google.firebase.firestore.AggregateField;
 import com.google.firebase.firestore.EventListener;
 import com.google.firebase.firestore.FirebaseFirestoreException;
@@ -47,7 +48,6 @@
 import com.google.firebase.firestore.remote.RemoteSerializer;
 import com.google.firebase.firestore.remote.RemoteStore;
 import com.google.firebase.firestore.util.AsyncQueue;
-import com.google.firebase.firestore.util.Function;
 import com.google.firebase.firestore.util.Logger;
 import com.google.firestore.v1.Value;
 import java.io.InputStream;
diff --git a/firebase-firestore/src/main/java/com/google/firebase/firestore/core/SyncEngine.java b/firebase-firestore/src/main/java/com/google/firebase/firestore/core/SyncEngine.java
index e9bb7bafea6..8b1c895ab0d 100644
--- a/firebase-firestore/src/main/java/com/google/firebase/firestore/core/SyncEngine.java
+++ b/firebase-firestore/src/main/java/com/google/firebase/firestore/core/SyncEngine.java
@@ -21,6 +21,7 @@
 import androidx.annotation.VisibleForTesting;
 import com.google.android.gms.tasks.Task;
 import com.google.android.gms.tasks.TaskCompletionSource;
+import com.google.common.base.Function;
 import com.google.firebase.database.collection.ImmutableSortedMap;
 import com.google.firebase.database.collection.ImmutableSortedSet;
 import com.google.firebase.firestore.AggregateField;
@@ -52,7 +53,6 @@
 import com.google.firebase.firestore.remote.RemoteStore;
 import com.google.firebase.firestore.remote.TargetChange;
 import com.google.firebase.firestore.util.AsyncQueue;
-import com.google.firebase.firestore.util.Function;
 import com.google.firebase.firestore.util.Logger;
 import com.google.firebase.firestore.util.Util;
 import com.google.firestore.v1.Value;
diff --git a/firebase-firestore/src/main/java/com/google/firebase/firestore/core/TransactionRunner.java b/firebase-firestore/src/main/java/com/google/firebase/firestore/core/TransactionRunner.java
index 28db0e6902e..fa15dc62496 100644
--- a/firebase-firestore/src/main/java/com/google/firebase/firestore/core/TransactionRunner.java
+++ b/firebase-firestore/src/main/java/com/google/firebase/firestore/core/TransactionRunner.java
@@ -17,6 +17,7 @@
 import androidx.annotation.NonNull;
 import com.google.android.gms.tasks.Task;
 import com.google.android.gms.tasks.TaskCompletionSource;
+import com.google.common.base.Function;
 import com.google.firebase.firestore.FirebaseFirestoreException;
 import com.google.firebase.firestore.TransactionOptions;
 import com.google.firebase.firestore.remote.Datastore;
@@ -24,7 +25,6 @@
 import com.google.firebase.firestore.util.AsyncQueue;
 import com.google.firebase.firestore.util.AsyncQueue.TimerId;
 import com.google.firebase.firestore.util.ExponentialBackoff;
-import com.google.firebase.firestore.util.Function;
 
 /** TransactionRunner encapsulates the logic needed to run and retry transactions with backoff. */
 public class TransactionRunner<TResult> {
diff --git a/firebase-firestore/src/main/java/com/google/firebase/firestore/local/SQLitePersistence.java b/firebase-firestore/src/main/java/com/google/firebase/firestore/local/SQLitePersistence.java
index b9c89d3cb8b..eab22c985d3 100644
--- a/firebase-firestore/src/main/java/com/google/firebase/firestore/local/SQLitePersistence.java
+++ b/firebase-firestore/src/main/java/com/google/firebase/firestore/local/SQLitePersistence.java
@@ -30,13 +30,13 @@
 import android.database.sqlite.SQLiteTransactionListener;
 import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
+import com.google.common.base.Function;
 import com.google.firebase.firestore.FirebaseFirestoreException;
 import com.google.firebase.firestore.FirebaseFirestoreException.Code;
 import com.google.firebase.firestore.auth.User;
 import com.google.firebase.firestore.model.DatabaseId;
 import com.google.firebase.firestore.util.Consumer;
 import com.google.firebase.firestore.util.FileUtil;
-import com.google.firebase.firestore.util.Function;
 import com.google.firebase.firestore.util.Logger;
 import com.google.firebase.firestore.util.Supplier;
 import java.io.File;
diff --git a/firebase-firestore/src/main/java/com/google/firebase/firestore/local/SQLiteRemoteDocumentCache.java b/firebase-firestore/src/main/java/com/google/firebase/firestore/local/SQLiteRemoteDocumentCache.java
index b26f9601a81..5d7c48be64b 100644
--- a/firebase-firestore/src/main/java/com/google/firebase/firestore/local/SQLiteRemoteDocumentCache.java
+++ b/firebase-firestore/src/main/java/com/google/firebase/firestore/local/SQLiteRemoteDocumentCache.java
@@ -22,6 +22,7 @@
 
 import android.database.Cursor;
 import androidx.annotation.VisibleForTesting;
+import com.google.common.base.Function;
 import com.google.firebase.Timestamp;
 import com.google.firebase.database.collection.ImmutableSortedMap;
 import com.google.firebase.firestore.core.Query;
@@ -33,7 +34,6 @@
 import com.google.firebase.firestore.model.SnapshotVersion;
 import com.google.firebase.firestore.util.BackgroundQueue;
 import com.google.firebase.firestore.util.Executors;
-import com.google.firebase.firestore.util.Function;
 import com.google.protobuf.InvalidProtocolBufferException;
 import com.google.protobuf.MessageLite;
 import java.util.ArrayList;
diff --git a/firebase-firestore/src/main/java/com/google/firebase/firestore/util/Function.java b/firebase-firestore/src/main/java/com/google/firebase/firestore/util/Function.java
deleted file mode 100644
index 1f73d37cead..00000000000
--- a/firebase-firestore/src/main/java/com/google/firebase/firestore/util/Function.java
+++ /dev/null
@@ -1,75 +0,0 @@
-// Copyright 2020 Google LLC
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package com.google.firebase.firestore.util;
-
-import javax.annotation.Nullable;
-
-//  This is a copy of
-//  https://github.com/google/guava/blob/master/guava/src/com/google/common/base/Function.java.
-/**
- * Determines an output value based on an input value; a pre-Java-8 version of {@link
- * java.util.function.Function java.util.function.Function}.
- *
- * <p>See the Guava User Guide article on <a
- * href="https://github.com/google/guava/wiki/FunctionalExplained">the use of {@code Function}</a>.
- *
- * <h3>For Java 8+ users</h3>
- *
- * <p>This interface is now a legacy type. Use {@code java.util.function.Function} (or the
- * appropriate primitive specialization such as {@code ToIntFunction}) instead whenever possible.
- * Otherwise, at least reduce <i>explicit</i> dependencies on this type by using lambda expressions
- * or method references instead of classes, leaving your code easier to migrate in the future.
- *
- * <p>To use an existing function (say, named {@code function}) in a context where the <i>other
- * type</i> of function is expected, use the method reference {@code function::apply}. A future
- * version of {@code com.google.firebase.firestore.util.Function} will be made to <i>extend</i>
- * {@code java.util.function.Function}, making conversion code necessary only in one direction. At
- * that time, this interface will be officially discouraged.
- *
- * @author Kevin Bourrillion
- * @since 2.0
- */
-public interface Function<F, T> {
-  /**
-   * Returns the result of applying this function to {@code input}. This method is <i>generally
-   * expected</i>, but not absolutely required, to have the following properties:
-   *
-   * <ul>
-   *   <li>Its execution does not cause any observable side effects.
-   *   <li>The computation is <i>consistent with equals</i>; that is, {@link Objects#equal
-   *       Objects.equal}{@code (a, b)} implies that {@code Objects.equal(function.apply(a),
-   *       function.apply(b))}.
-   * </ul>
-   *
-   * @throws NullPointerException if {@code input} is null and this function does not accept null
-   *     arguments
-   */
-  @Nullable
-  T apply(@Nullable F input);
-
-  /**
-   * <i>May</i> return {@code true} if {@code object} is a {@code Function} that behaves identically
-   * to this function.
-   *
-   * <p><b>Warning: do not depend</b> on the behavior of this method.
-   *
-   * <p>Historically, {@code Function} instances in this library have implemented this method to
-   * recognize certain cases where distinct {@code Function} instances would in fact behave
-   * identically. However, as code migrates to {@code java.util.function}, that behavior will
-   * disappear. It is best not to depend on it.
-   */
-  @Override
-  boolean equals(@Nullable Object object);
-}