diff --git a/dev/src/index.ts b/dev/src/index.ts
index a70de3a84..791b2e4a7 100644
--- a/dev/src/index.ts
+++ b/dev/src/index.ts
@@ -432,6 +432,14 @@ export class Firestore implements firestore.Firestore {
    */
   private _projectId: string | undefined = undefined;
 
+  /**
+   * The database ID provided via `.settings()`.
+   *
+   * @private
+   * @internal
+   */
+  private _databaseId: string | undefined = undefined;
+
   /**
    * Count of listeners that have been registered on the client.
    *
@@ -571,6 +579,9 @@ export class Firestore implements firestore.Firestore {
   settings(settings: firestore.Settings): void {
     validateObject('settings', settings);
     validateString('settings.projectId', settings.projectId, {optional: true});
+    validateString('settings.databaseId', settings.databaseId, {
+      optional: true,
+    });
 
     if (this._settingsFrozen) {
       throw new Error(
@@ -591,6 +602,11 @@ export class Firestore implements firestore.Firestore {
       this._projectId = settings.projectId;
     }
 
+    if (settings.databaseId !== undefined) {
+      validateString('settings.databaseId', settings.databaseId);
+      this._databaseId = settings.databaseId;
+    }
+
     let url: URL | null = null;
 
     // If the environment variable is set, it should always take precedence
@@ -678,6 +694,16 @@ export class Firestore implements firestore.Firestore {
     return this._projectId;
   }
 
+  /**
+   * Returns the Database ID for this Firestore instance.
+   *
+   * @private
+   * @internal
+   */
+  get databaseId(): string {
+    return this._databaseId || DEFAULT_DATABASE_ID;
+  }
+
   /**
    * Returns the root path of the database. Validates that
    * `initializeIfNeeded()` was called before.
@@ -686,7 +712,7 @@ export class Firestore implements firestore.Firestore {
    * @internal
    */
   get formattedName(): string {
-    return `projects/${this.projectId}/databases/${DEFAULT_DATABASE_ID}`;
+    return `projects/${this.projectId}/databases/${this.databaseId}`;
   }
 
   /**
diff --git a/dev/test/index.ts b/dev/test/index.ts
index a3cf866fe..96db12f8c 100644
--- a/dev/test/index.ts
+++ b/dev/test/index.ts
@@ -304,6 +304,7 @@ describe('instantiation', () => {
 
     /* eslint-disable @typescript-eslint/no-explicit-any */
     expect((firestore as any)._settings.projectId).to.equal(PROJECT_ID);
+    expect((firestore as any)._settings.databaseId).to.be.undefined;
     expect((firestore as any)._settings.foo).to.equal('bar');
     /* eslint-enable @typescript-eslint/no-explicit-any */
   });
@@ -343,6 +344,23 @@ describe('instantiation', () => {
     );
   });
 
+  it('validates database ID is string', () => {
+    expect(() => {
+      const settings = {...DEFAULT_SETTINGS, databaseId: 1337};
+      new Firestore.Firestore(settings as InvalidApiUsage);
+    }).to.throw(
+      'Value for argument "settings.databaseId" is not a valid string.'
+    );
+
+    expect(() => {
+      new Firestore.Firestore(DEFAULT_SETTINGS).settings({
+        databaseId: 1337,
+      } as InvalidApiUsage);
+    }).to.throw(
+      'Value for argument "settings.databaseId" is not a valid string.'
+    );
+  });
+
   it('validates ssl is a boolean', () => {
     const invalidValues = ['true', 1337];
 
@@ -548,11 +566,14 @@ describe('instantiation', () => {
     new Firestore.Firestore({maxIdleChannels: 1});
   });
 
-  it('uses project id from constructor', () => {
-    const firestore = new Firestore.Firestore({projectId: 'foo'});
+  it('uses project id and database id from constructor', () => {
+    const firestore = new Firestore.Firestore({
+      projectId: 'foo',
+      databaseId: 'bar',
+    });
 
     return expect(firestore.formattedName).to.equal(
-      'projects/foo/databases/(default)'
+      'projects/foo/databases/bar'
     );
   });
 
@@ -571,7 +592,7 @@ describe('instantiation', () => {
     });
   });
 
-  it('uses project ID from settings()', () => {
+  it('uses project ID from settings() and default database ID', () => {
     const firestore = new Firestore.Firestore({
       sslCreds: grpc.credentials.createInsecure(),
     });
@@ -583,6 +604,18 @@ describe('instantiation', () => {
     );
   });
 
+  it('uses database ID and database ID from settings()', () => {
+    const firestore = new Firestore.Firestore({
+      sslCreds: grpc.credentials.createInsecure(),
+    });
+
+    firestore.settings({projectId: PROJECT_ID, databaseId: 'bar'});
+
+    expect(firestore.formattedName).to.equal(
+      `projects/${PROJECT_ID}/databases/bar`
+    );
+  });
+
   it('handles error from project ID detection', () => {
     return createInstance(
       {
diff --git a/types/firestore.d.ts b/types/firestore.d.ts
index 2e32bc40a..22e14e583 100644
--- a/types/firestore.d.ts
+++ b/types/firestore.d.ts
@@ -227,6 +227,13 @@ declare namespace FirebaseFirestore {
      */
     projectId?: string;
 
+    /**
+     * The database name. If omitted, the default database will be used.
+     *
+     * @internal
+     */
+    databaseId?: string;
+
     /** The hostname to connect to. */
     host?: string;