diff --git a/src/common/analytics/entities.ts b/src/common/analytics/entities.ts
index 36d9104b..7e844416 100644
--- a/src/common/analytics/entities.ts
+++ b/src/common/analytics/entities.ts
@@ -16,6 +16,7 @@ export enum EVENT_NAME {
   FILTER_SELECTED = "filter_selected",
   INDEX_ANALYZE_IN_TERRA_REQUESTED = "index_analyze_in_terra_requested",
   INDEX_FILE_MANIFEST_REQUESTED = "index_file_manifest_requested",
+  LOGIN = "login", // GA4 recommended event name; not past tense to match GA4 standard.
 }
 
 /**
@@ -82,4 +83,5 @@ export type EventParams = {
   [EVENT_NAME.INDEX_FILE_MANIFEST_REQUESTED]: {
     [EVENT_PARAM.ENTITY_NAME]: string;
   };
+  [EVENT_NAME.LOGIN]: { [EVENT_PARAM.TOOL_NAME]: string };
 };
diff --git a/src/google/provider.tsx b/src/google/provider.tsx
index 03e4b85f..26fa6e57 100644
--- a/src/google/provider.tsx
+++ b/src/google/provider.tsx
@@ -8,6 +8,7 @@ import { useCredentialsReducer } from "../auth/hooks/useCredentialsReducer";
 import { useSessionIdleTimer } from "../auth/hooks/useSessionIdleTimer";
 import { useSessionActive } from "../hooks/authentication/session/useSessionActive";
 import { useSessionCallbackUrl } from "../hooks/authentication/session/useSessionCallbackUrl";
+import { useLoginTracking } from "../hooks/authentication/useLoginTracking";
 import { AUTH_STATE, AUTHENTICATION_STATE } from "./constants";
 import { useGoogleSignInService } from "./hooks/useGoogleSignInService";
 import { useTokenReducer } from "./hooks/useTokenReducer";
@@ -41,6 +42,7 @@ export function GoogleSignInAuthenticationProvider({
   const { authDispatch, authState } = authReducer;
   const { isAuthenticated } = authState;
   const { authenticationState } = authenticationReducer;
+  useLoginTracking(isAuthenticated, authState.status);
   useSessionActive(authState, authenticationState);
   useSessionIdleTimer({
     disabled: !isAuthenticated,
diff --git a/src/hooks/authentication/useLoginTracking.ts b/src/hooks/authentication/useLoginTracking.ts
new file mode 100644
index 00000000..85e5b12c
--- /dev/null
+++ b/src/hooks/authentication/useLoginTracking.ts
@@ -0,0 +1,28 @@
+import { useEffect, useRef } from "react";
+import { AUTH_STATUS } from "../../auth/types/auth";
+import { track } from "../../common/analytics/analytics";
+import { EVENT_NAME, EVENT_PARAM } from "../../common/analytics/entities";
+import { GOOGLE_SIGN_IN_PROVIDER_ID } from "../../google/constants";
+
+/**
+ * Tracks a GA4 login event when the user transitions from unauthenticated to authenticated.
+ * Does not fire during initial session hydration or on mount if already authenticated.
+ * @param isAuthenticated - Current authentication state.
+ * @param status - Current auth status; tracking only begins after status has settled.
+ * @returns void.
+ */
+export function useLoginTracking(
+  isAuthenticated: boolean,
+  status: AUTH_STATUS,
+): void {
+  const wasAuthenticated = useRef<boolean | undefined>(undefined);
+  useEffect(() => {
+    if (status !== AUTH_STATUS.SETTLED) return;
+    if (wasAuthenticated.current === false && isAuthenticated) {
+      track(EVENT_NAME.LOGIN, {
+        [EVENT_PARAM.TOOL_NAME]: GOOGLE_SIGN_IN_PROVIDER_ID,
+      });
+    }
+    wasAuthenticated.current = isAuthenticated;
+  }, [isAuthenticated, status]);
+}
diff --git a/src/nextauth/provider.tsx b/src/nextauth/provider.tsx
index 0b140967..b031ca62 100644
--- a/src/nextauth/provider.tsx
+++ b/src/nextauth/provider.tsx
@@ -6,6 +6,7 @@ import { useAuthenticationReducer } from "../auth/hooks/useAuthenticationReducer
 import { useAuthReducer } from "../auth/hooks/useAuthReducer";
 import { useSessionIdleTimer } from "../auth/hooks/useSessionIdleTimer";
 import { useSessionCallbackUrl } from "../hooks/authentication/session/useSessionCallbackUrl";
+import { useLoginTracking } from "../hooks/authentication/useLoginTracking";
 import { useNextAuthService } from "./hooks/useNextAuthService";
 import { SessionController } from "./session-controller";
 import { NextAuthAuthenticationProviderProps } from "./types";
@@ -30,6 +31,7 @@ export function NextAuthAuthenticationProvider({
   const service = useNextAuthService();
   const { authDispatch, authState } = authReducer;
   const { isAuthenticated } = authState;
+  useLoginTracking(isAuthenticated, authState.status);
   const { callbackUrl } = useSessionCallbackUrl();
   useSessionIdleTimer({
     crossTab: true,
diff --git a/tests/useLoginTracking.test.ts b/tests/useLoginTracking.test.ts
new file mode 100644
index 00000000..e0781d03
--- /dev/null
+++ b/tests/useLoginTracking.test.ts
@@ -0,0 +1,75 @@
+import { jest } from "@jest/globals";
+import { renderHook } from "@testing-library/react";
+import { AUTH_STATUS } from "../src/auth/types/auth";
+
+const mockTrack = jest.fn();
+
+jest.unstable_mockModule("../src/common/analytics/analytics", () => ({
+  track: mockTrack,
+}));
+
+const { useLoginTracking } =
+  await import("../src/hooks/authentication/useLoginTracking");
+
+const SETTLED = AUTH_STATUS.SETTLED;
+const PENDING = AUTH_STATUS.PENDING;
+
+describe("useLoginTracking", () => {
+  beforeEach(() => {
+    mockTrack.mockReset();
+  });
+
+  test("does not fire on initial mount when unauthenticated", () => {
+    renderHook(() => useLoginTracking(false, SETTLED));
+    expect(mockTrack).not.toHaveBeenCalled();
+  });
+
+  test("does not fire on initial mount when already authenticated", () => {
+    renderHook(() => useLoginTracking(true, SETTLED));
+    expect(mockTrack).not.toHaveBeenCalled();
+  });
+
+  test("fires login event on transition from unauthenticated to authenticated", () => {
+    const { rerender } = renderHook(
+      ({ isAuthenticated, status }) =>
+        useLoginTracking(isAuthenticated, status),
+      { initialProps: { isAuthenticated: false, status: SETTLED } },
+    );
+    rerender({ isAuthenticated: true, status: SETTLED });
+    expect(mockTrack).toHaveBeenCalledTimes(1);
+    expect(mockTrack).toHaveBeenCalledWith("login", { tool_name: "google" });
+  });
+
+  test("does not fire on transition from authenticated to unauthenticated", () => {
+    const { rerender } = renderHook(
+      ({ isAuthenticated, status }) =>
+        useLoginTracking(isAuthenticated, status),
+      { initialProps: { isAuthenticated: true, status: SETTLED } },
+    );
+    rerender({ isAuthenticated: false, status: SETTLED });
+    expect(mockTrack).not.toHaveBeenCalled();
+  });
+
+  test("fires for each login transition", () => {
+    const { rerender } = renderHook(
+      ({ isAuthenticated, status }) =>
+        useLoginTracking(isAuthenticated, status),
+      { initialProps: { isAuthenticated: false, status: SETTLED } },
+    );
+    rerender({ isAuthenticated: true, status: SETTLED });
+    rerender({ isAuthenticated: false, status: SETTLED });
+    rerender({ isAuthenticated: true, status: SETTLED });
+    expect(mockTrack).toHaveBeenCalledTimes(2);
+  });
+
+  test("does not fire during session hydration when status is pending", () => {
+    const { rerender } = renderHook(
+      ({ isAuthenticated, status }) =>
+        useLoginTracking(isAuthenticated, status),
+      { initialProps: { isAuthenticated: false, status: PENDING } },
+    );
+    // Session hydrates: isAuthenticated becomes true while status settles.
+    rerender({ isAuthenticated: true, status: SETTLED });
+    expect(mockTrack).not.toHaveBeenCalled();
+  });
+});