diff --git a/.changeset/neat-pants-wonder.md b/.changeset/neat-pants-wonder.md
new file mode 100644
index 00000000000..76da28c3718
--- /dev/null
+++ b/.changeset/neat-pants-wonder.md
@@ -0,0 +1,5 @@
+---
+"@firebase/auth": patch
+---
+
+Add missing phone FACTOR_ID static property to the PhoneMultiFactorGenerator class
diff --git a/common/api-review/auth.api.md b/common/api-review/auth.api.md
index f0532091bbe..9fc9d58d565 100644
--- a/common/api-review/auth.api.md
+++ b/common/api-review/auth.api.md
@@ -596,6 +596,7 @@ export interface PhoneMultiFactorEnrollInfoOptions {
 // @public
 export class PhoneMultiFactorGenerator {
     static assertion(credential: PhoneAuthCredential): PhoneMultiFactorAssertion;
+    static FACTOR_ID: string;
 }
 
 // @public
diff --git a/packages/auth/src/platform_browser/mfa/assertions/phone.ts b/packages/auth/src/platform_browser/mfa/assertions/phone.ts
index 91633f82cc9..7b62b7f6079 100644
--- a/packages/auth/src/platform_browser/mfa/assertions/phone.ts
+++ b/packages/auth/src/platform_browser/mfa/assertions/phone.ts
@@ -90,4 +90,9 @@ export class PhoneMultiFactorGenerator {
   static assertion(credential: PhoneAuthCredential): PhoneMultiFactorAssertion {
     return PhoneMultiFactorAssertionImpl._fromCredential(credential);
   }
+
+  /**
+   * The identifier of the phone second factor: `phone`.
+   */
+  static FACTOR_ID = 'phone';
 }