diff --git a/app/asr/router.py b/app/asr/router.py
index d353ea4..bf8b689 100644
--- a/app/asr/router.py
+++ b/app/asr/router.py
@@ -24,6 +24,7 @@ from asr.config import (
 )
 
 router = APIRouter()
+ws_router = APIRouter()
 
 BACKENDS = {
     "faster-whisper": FASTER_WHISPER_URL,
@@ -267,8 +268,11 @@ async def _send_chunk(wav_bytes: bytes, *, model: str, language: str, beam_size:
     return resp.json()
 
 
-@router.websocket("/ws/realtime")
+@ws_router.websocket("/ws/realtime")
 async def realtime_ws(websocket: WebSocket) -> None:
+    if not websocket.session.get("user"):
+        await websocket.close(code=4401)
+        return
     await websocket.accept()
 
     audio_buf = bytearray()
diff --git a/app/core/auth.py b/app/core/auth.py
new file mode 100644
index 0000000..900231c
--- /dev/null
+++ b/app/core/auth.py
@@ -0,0 +1,66 @@
+from __future__ import annotations
+
+from typing import Any, Dict
+
+from authlib.integrations.starlette_client import OAuth
+from fastapi import APIRouter, HTTPException, Request
+from fastapi.responses import RedirectResponse
+
+from core.config import env_str
+
+OIDC_ISSUER = env_str("ASR_V2_OIDC_ISSUER", "")
+OIDC_CLIENT_ID = env_str("ASR_V2_OIDC_CLIENT_ID", "")
+OIDC_CLIENT_SECRET = env_str("ASR_V2_OIDC_CLIENT_SECRET", "")
+OIDC_REDIRECT_URI = env_str("ASR_V2_OIDC_REDIRECT_URI", "")
+SESSION_SECRET_KEY = env_str("ASR_V2_SESSION_SECRET_KEY", "")
+
+oauth = OAuth()
+oauth.register(
+    name="authentik",
+    client_id=OIDC_CLIENT_ID,
+    client_secret=OIDC_CLIENT_SECRET,
+    server_metadata_url=f"{OIDC_ISSUER}.well-known/openid-configuration",
+    client_kwargs={"scope": "openid email profile"},
+)
+
+router = APIRouter()
+
+
+@router.get("/login")
+async def login(request: Request, next: str = "/"):
+    request.session["next"] = next if next.startswith("/") else "/"
+    return await oauth.authentik.authorize_redirect(request, OIDC_REDIRECT_URI)
+
+
+@router.get("/callback")
+async def callback(request: Request):
+    try:
+        token = await oauth.authentik.authorize_access_token(request)
+    except Exception as exc:
+        raise HTTPException(status_code=401, detail=f"로그인 실패: {exc}") from exc
+
+    userinfo = token.get("userinfo") or {}
+    request.session["user"] = {
+        "sub": userinfo.get("sub"),
+        "username": userinfo.get("preferred_username") or userinfo.get("nickname"),
+        "email": userinfo.get("email"),
+        "name": userinfo.get("name"),
+    }
+    next_path = request.session.pop("next", "/") or "/"
+    return RedirectResponse(url=next_path)
+
+
+@router.get("/logout")
+async def logout(request: Request):
+    request.session.pop("user", None)
+    return RedirectResponse(url="/")
+
+
+def require_login(request: Request) -> Dict[str, Any]:
+    user = request.session.get("user")
+    if not user:
+        raise HTTPException(
+            status_code=303,
+            headers={"Location": f"/auth/login?next={request.url.path}"},
+        )
+    return user
diff --git a/app/main.py b/app/main.py
index 6fa6505..e3a6cd7 100644
--- a/app/main.py
+++ b/app/main.py
@@ -3,16 +3,27 @@ from __future__ import annotations
 from pathlib import Path
 from typing import Any, Dict
 
-from fastapi import FastAPI
+from fastapi import Depends, FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import FileResponse, HTMLResponse, JSONResponse
 from fastapi.staticfiles import StaticFiles
+from starlette.middleware.sessions import SessionMiddleware
 
 from asr.config import ensure_runtime_dirs
 from asr.router import router as asr_router
+from asr.router import ws_router as asr_ws_router
+from core.auth import SESSION_SECRET_KEY, require_login
+from core.auth import router as auth_router
 from tts.router import router as tts_router
 
 app = FastAPI(title="ASR/TTS Gateway", docs_url="/docs", redoc_url="/redoc")
+app.add_middleware(
+    SessionMiddleware,
+    secret_key=SESSION_SECRET_KEY,
+    same_site="lax",
+    https_only=False,  # 아직 전용 도메인/TLS가 없어 내부 IP:포트(http)로 접근하기 때문
+    max_age=14 * 24 * 3600,
+)
 app.add_middleware(
     CORSMiddleware,
     allow_origins=["*"],
@@ -23,8 +34,10 @@ app.add_middleware(
 
 UI_DIR = Path("/app/ui")
 
-app.include_router(asr_router, prefix="/asr", tags=["asr"])
-app.include_router(tts_router, prefix="/tts", tags=["tts"])
+app.include_router(auth_router, prefix="/auth", tags=["auth"])
+app.include_router(asr_router, prefix="/asr", tags=["asr"], dependencies=[Depends(require_login)])
+app.include_router(asr_ws_router, prefix="/asr", tags=["asr"])  # 인증은 핸들러 내부에서 세션으로 직접 체크
+app.include_router(tts_router, prefix="/tts", tags=["tts"], dependencies=[Depends(require_login)])
 
 
 @app.on_event("startup")
@@ -40,7 +53,7 @@ def health() -> Dict[str, Any]:
     return {"status": "ok", "ui_installed": UI_DIR.exists(), "api": "/docs"}
 
 
-@app.get("/", response_class=HTMLResponse)
+@app.get("/", response_class=HTMLResponse, dependencies=[Depends(require_login)])
 def root() -> Any:
     index = UI_DIR / "index.html"
     if index.exists():
diff --git a/app/ui/assets/css/styles.css b/app/ui/assets/css/styles.css
index e5e2d2e..10013b8 100644
--- a/app/ui/assets/css/styles.css
+++ b/app/ui/assets/css/styles.css
@@ -8,6 +8,8 @@ body {
 .wrap { max-width: 1100px; margin: 0 auto; padding: 24px; }
 .page-header { margin-bottom: 8px; }
 .page-header h1 { margin: 0 0 4px; }
+.header-row { display: flex; align-items: center; justify-content: space-between; gap: 12px; }
+.logout-link { text-decoration: none; flex-shrink: 0; display: inline-block; }
 .muted { color: #aab3cf; margin: 0; }
 .small { font-size: 0.87em; }
 .mono { font-family: monospace; }
diff --git a/app/ui/index.html b/app/ui/index.html
index ec5dddd..9893f0b 100644
--- a/app/ui/index.html
+++ b/app/ui/index.html
@@ -9,8 +9,13 @@
 <body>
   <main class="wrap">
     <header class="page-header">
-      <h1>ASR · TTS 콘솔</h1>
-      <p class="muted">음성 인식(ASR)과 음성 합성(TTS)을 한 곳에서</p>
+      <div class="header-row">
+        <div>
+          <h1>ASR · TTS 콘솔</h1>
+          <p class="muted">음성 인식(ASR)과 음성 합성(TTS)을 한 곳에서</p>
+        </div>
+        <a href="/auth/logout" class="btn-secondary logout-link" title="로그아웃">로그아웃</a>
+      </div>
     </header>
 
     <div class="tab-group tab-group--top">
diff --git a/envs/gateway.txt b/envs/gateway.txt
index d63113d..aa15656 100644
--- a/envs/gateway.txt
+++ b/envs/gateway.txt
@@ -5,3 +5,5 @@ httpx==0.27.2
 websockets>=12.0
 jinja2==3.1.4
 numpy
+authlib==1.3.2
+itsdangerous==2.2.0