diff --git a/Assets/Scripts/GameManager.cs b/Assets/Scripts/GameManager.cs
new file mode 100644
index 00000000..b60f023a
--- /dev/null
+++ b/Assets/Scripts/GameManager.cs
@@ -0,0 +1,515 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using UnityEngine;
+using UnityEngine.SceneManagement;
+using Unity.Netcode;
+using Colosseum.Player;
+using Colosseum.Enemy;
+
+namespace Colosseum
+{
+    /// <summary>
+    /// 게임 상태 열거형
+    /// </summary>
+    public enum GameState
+    {
+        Waiting,    // 대기 중
+        Playing,    // 게임 진행 중
+        GameOver,   // 게임 오버
+        Victory     // 승리
+    }
+
+    /// <summary>
+    /// 게임 전체를 관리하는 매니저.
+    /// 게임 상태, 플레이어 사망 체크, 승리/패배 조건을 처리합니다.
+    /// </summary>
+    public class GameManager : NetworkBehaviour
+    {
+        [Header("UI Prefabs")]
+        [Tooltip("게임 오버 UI 프리팹")]
+        [SerializeField] private GameObject gameOverUIPrefab;
+
+        [Tooltip("승리 UI 프리팹")]
+        [SerializeField] private GameObject victoryUIPrefab;
+
+        [Tooltip("승리 연출 이펙트 프리팹")]
+        [SerializeField] private GameObject victoryEffectPrefab;
+
+        [Header("Settings")]
+        [Tooltip("게임 오버 후 재시작까지 대기 시간")]
+        [SerializeField] private float gameOverRestartDelay = 5f;
+
+        [Tooltip("승리 후 로비로 이동까지 대기 시간")]
+        [SerializeField] private float victoryToLobbyDelay = 5f;
+
+        [Header("Debug")]
+        [SerializeField] private bool debugMode = true;
+
+        // 싱글톤
+        public static GameManager Instance { get; private set; }
+
+        // 게임 상태
+        private NetworkVariable<GameState> currentState = new NetworkVariable<GameState>(GameState.Waiting);
+
+        // 인스턴스화된 UI
+        private GameObject gameOverUIInstance;
+        private GameObject victoryUIInstance;
+        private GameObject victoryEffectInstance;
+
+        // 이벤트
+        public event Action<GameState> OnGameStateChanged;
+        public event Action OnGameOver;
+        public event Action OnVictory;
+
+        // Properties
+        public GameState CurrentState => currentState.Value;
+        public bool IsGameOver => currentState.Value == GameState.GameOver;
+        public bool IsVictory => currentState.Value == GameState.Victory;
+
+        private void Awake()
+        {
+            // 싱글톤 설정
+            if (Instance != null && Instance != this)
+            {
+                Destroy(gameObject);
+                return;
+            }
+            Instance = this;
+        }
+
+        public override void OnNetworkSpawn()
+        {
+            currentState.OnValueChanged += HandleGameStateChanged;
+
+            // 네트워크 씬 로드 이벤트 구독
+            if (NetworkManager.Singleton.SceneManager != null)
+            {
+                NetworkManager.Singleton.SceneManager.OnLoadEventCompleted += OnSceneLoadCompleted;
+            }
+
+            // UI 인스턴스화 (모든 클라이언트에서)
+            SpawnUI();
+
+            if (IsServer)
+            {
+                // 플레이어 사망 이벤트 구독
+                StartCoroutine(WaitForPlayersAndSubscribe());
+
+                // 보스 사망 이벤트 구독
+                SubscribeToBossEvents();
+            }
+        }
+
+        private void OnSceneLoadCompleted(string sceneName, LoadSceneMode loadSceneMode, List<ulong> clientsCompleted, List<ulong> clientsTimedOut)
+        {
+            if (loadSceneMode == LoadSceneMode.Single)
+            {
+                if (debugMode)
+                {
+                    Debug.Log($"[GameManager] Scene loaded: {sceneName}");
+                }
+
+                // 씬 로드 완료 시 플레이어 리스폰
+                if (IsServer)
+                {
+                    RespawnAllPlayersClientRpc();
+                }
+            }
+        }
+
+        [Rpc(SendTo.ClientsAndHost)]
+        private void RespawnAllPlayersClientRpc()
+        {
+            // 모든 플레이어 리스폰
+            var players = FindObjectsByType<PlayerNetworkController>(FindObjectsSortMode.None);
+            foreach (var player in players)
+            {
+                player.Respawn();
+            }
+
+            // 카메라 재설정
+            var playerMovement = FindObjectsByType<PlayerMovement>(FindObjectsSortMode.None);
+            foreach (var movement in playerMovement)
+            {
+                movement.RefreshCamera();
+            }
+        }
+
+        public override void OnNetworkDespawn()
+        {
+            currentState.OnValueChanged -= HandleGameStateChanged;
+
+            // 네트워크 씬 로드 이벤트 구독 해제
+            if (NetworkManager.Singleton.SceneManager != null)
+            {
+                NetworkManager.Singleton.SceneManager.OnLoadEventCompleted -= OnSceneLoadCompleted;
+            }
+
+            // UI 정리
+            CleanupUI();
+
+            if (IsServer)
+            {
+                UnsubscribeFromPlayerEvents();
+                UnsubscribeFromBossEvents();
+            }
+        }
+
+        #region UI Management
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
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+
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+
+
+
+
+
+
+        /// <summary>
+        /// UI 프리팹 인스턴스화
+        /// </summary>
+        private void SpawnUI()
+        {
+            // Canvas 찾기 또는 생성
+            Canvas canvas = FindOrCreateCanvas();
+
+            // 게임 오버 UI
+            if (gameOverUIPrefab != null)
+            {
+                gameOverUIInstance = Instantiate(gameOverUIPrefab, canvas.transform);
+                gameOverUIInstance.name = "GameOverUI";
+                gameOverUIInstance.SetActive(false);
+
+                if (debugMode)
+                {
+                    Debug.Log("[GameManager] GameOverUI instantiated");
+                }
+            }
+
+            // 승리 UI
+            if (victoryUIPrefab != null)
+            {
+                victoryUIInstance = Instantiate(victoryUIPrefab, canvas.transform);
+                victoryUIInstance.name = "VictoryUI";
+                victoryUIInstance.SetActive(false);
+
+                if (debugMode)
+                {
+                    Debug.Log("[GameManager] VictoryUI instantiated");
+                }
+            }
+
+            // 승리 연출 이펙트
+            if (victoryEffectPrefab != null)
+            {
+                victoryEffectInstance = Instantiate(victoryEffectPrefab);
+                victoryEffectInstance.name = "VictoryEffect";
+                victoryEffectInstance.SetActive(false);
+
+                if (debugMode)
+                {
+                    Debug.Log("[GameManager] VictoryEffect instantiated");
+                }
+            }
+        }
+
+        /// <summary>
+        /// Canvas 찾기 또는 생성
+        /// </summary>
+        private Canvas FindOrCreateCanvas()
+        {
+            // 기존 Canvas 찾기
+            Canvas canvas = FindFirstObjectByType<Canvas>();
+
+            if (canvas == null)
+            {
+                // 새 Canvas 생성
+                var canvasObject = new GameObject("GameUI Canvas");
+                canvas = canvasObject.AddComponent<Canvas>();
+                canvas.renderMode = RenderMode.ScreenSpaceOverlay;
+                canvasObject.AddComponent<UnityEngine.UI.CanvasScaler>();
+                canvasObject.AddComponent<UnityEngine.UI.GraphicRaycaster>();
+
+                if (debugMode)
+                {
+                    Debug.Log("[GameManager] Created new Canvas");
+                }
+            }
+
+            return canvas;
+        }
+
+        /// <summary>
+        /// UI 정리
+        /// </summary>
+        private void CleanupUI()
+        {
+            if (gameOverUIInstance != null)
+            {
+                Destroy(gameOverUIInstance);
+            }
+
+            if (victoryUIInstance != null)
+            {
+                Destroy(victoryUIInstance);
+            }
+
+            if (victoryEffectInstance != null)
+            {
+                Destroy(victoryEffectInstance);
+            }
+        }
+
+        #endregion
+
+        private void HandleGameStateChanged(GameState oldValue, GameState newValue)
+        {
+            OnGameStateChanged?.Invoke(newValue);
+
+            // UI 활성화/비활성화
+            UpdateUIVisibility(newValue);
+
+            if (debugMode)
+            {
+                Debug.Log($"[GameManager] State changed: {oldValue} -> {newValue}");
+            }
+        }
+
+        private void UpdateUIVisibility(GameState state)
+        {
+            // 게임 오버 UI
+            if (gameOverUIInstance != null)
+            {
+                gameOverUIInstance.SetActive(state == GameState.GameOver);
+            }
+
+            // 승리 UI
+            if (victoryUIInstance != null)
+            {
+                victoryUIInstance.SetActive(state == GameState.Victory);
+            }
+
+            // 승리 연출
+            if (victoryEffectInstance != null && state == GameState.Victory)
+            {
+                victoryEffectInstance.SetActive(true);
+            }
+        }
+
+        #region Player Death Tracking
+
+        private List<PlayerNetworkController> alivePlayers = new List<PlayerNetworkController>();
+
+        private IEnumerator WaitForPlayersAndSubscribe()
+        {
+            // 플레이어들이 스폰될 때까지 대기
+            yield return new WaitForSeconds(1f);
+
+            SubscribeToPlayerEvents();
+
+            // 게임 시작
+            SetGameState(GameState.Playing);
+        }
+
+        private void SubscribeToPlayerEvents()
+        {
+            var players = FindObjectsByType<PlayerNetworkController>(FindObjectsSortMode.None);
+            foreach (var player in players)
+            {
+                player.OnDeath += HandlePlayerDeath;
+                if (!player.IsDead)
+                {
+                    alivePlayers.Add(player);
+                }
+            }
+
+            if (debugMode)
+            {
+                Debug.Log($"[GameManager] Subscribed to {players.Length} players, {alivePlayers.Count} alive");
+            }
+        }
+
+        private void UnsubscribeFromPlayerEvents()
+        {
+            var players = FindObjectsByType<PlayerNetworkController>(FindObjectsSortMode.None);
+            foreach (var player in players)
+            {
+                player.OnDeath -= HandlePlayerDeath;
+            }
+            alivePlayers.Clear();
+        }
+
+        private void HandlePlayerDeath(PlayerNetworkController player)
+        {
+            alivePlayers.Remove(player);
+
+            if (debugMode)
+            {
+                Debug.Log($"[GameManager] Player died. Alive: {alivePlayers.Count}");
+            }
+
+            // 모든 플레이어 사망 체크
+            if (alivePlayers.Count == 0)
+            {
+                TriggerGameOver();
+            }
+        }
+
+        #endregion
+
+        #region Boss Death Tracking
+
+        private void SubscribeToBossEvents()
+        {
+            BossEnemy.OnBossSpawned += HandleBossSpawned;
+
+            // 이미 스폰된 보스가 있는지 확인
+            if (BossEnemy.ActiveBoss != null)
+            {
+                SubscribeToBossDeath(BossEnemy.ActiveBoss);
+            }
+        }
+
+        private void UnsubscribeFromBossEvents()
+        {
+            BossEnemy.OnBossSpawned -= HandleBossSpawned;
+        }
+
+        private void HandleBossSpawned(BossEnemy boss)
+        {
+            SubscribeToBossDeath(boss);
+
+            if (debugMode)
+            {
+                Debug.Log($"[GameManager] Boss spawned: {boss.name}");
+            }
+        }
+
+        private void SubscribeToBossDeath(BossEnemy boss)
+        {
+            boss.OnDeath += HandleBossDeath;
+        }
+
+        private void HandleBossDeath()
+        {
+            if (debugMode)
+            {
+                Debug.Log("[GameManager] Boss died!");
+            }
+
+            TriggerVictory();
+        }
+
+        #endregion
+
+        #region Game State Management
+
+        private void SetGameState(GameState newState)
+        {
+            if (!IsServer) return;
+
+            currentState.Value = newState;
+        }
+
+        /// <summary>
+        /// 게임 오버 처리 (서버에서만 실행)
+        /// </summary>
+        public void TriggerGameOver()
+        {
+            if (!IsServer || currentState.Value != GameState.Playing) return;
+
+            SetGameState(GameState.GameOver);
+            OnGameOver?.Invoke();
+
+            if (debugMode)
+            {
+                Debug.Log("[GameManager] Game Over!");
+            }
+
+            // N초 후 씬 재시작
+            StartCoroutine(RestartSceneAfterDelay(gameOverRestartDelay));
+        }
+
+        /// <summary>
+        /// 승리 처리 (서버에서만 실행)
+        /// </summary>
+        public void TriggerVictory()
+        {
+            if (!IsServer || currentState.Value != GameState.Playing) return;
+
+            SetGameState(GameState.Victory);
+            OnVictory?.Invoke();
+
+            if (debugMode)
+            {
+                Debug.Log("[GameManager] Victory!");
+            }
+
+            // N초 후 씬 재시작 (또는 로비로 이동)
+            StartCoroutine(RestartSceneAfterDelay(victoryToLobbyDelay));
+        }
+
+        private IEnumerator RestartSceneAfterDelay(float delay)
+        {
+            yield return new WaitForSeconds(delay);
+
+            // 현재 씬 다시 로드
+            string currentScene = SceneManager.GetActiveScene().name;
+
+            if (IsServer)
+            {
+                // 네트워크 씬 관리 사용
+                NetworkManager.Singleton.SceneManager.LoadScene(currentScene, LoadSceneMode.Single);
+            }
+        }
+
+        #endregion
+
+        #region Utility
+
+        /// <summary>
+        /// 살아있는 플레이어 목록 반환
+        /// </summary>
+        public List<PlayerNetworkController> GetAlivePlayers()
+        {
+            return alivePlayers.Where(p => p != null && !p.IsDead).ToList();
+        }
+
+        /// <summary>
+        /// 랜덤한 살아있는 플레이어 반환 (관전용)
+        /// </summary>
+        public PlayerNetworkController GetRandomAlivePlayer()
+        {
+            var alive = GetAlivePlayers();
+            if (alive.Count == 0) return null;
+
+            return alive[UnityEngine.Random.Range(0, alive.Count)];
+        }
+
+        #endregion
+    }
+}
diff --git a/Assets/Scripts/GameManager.cs.meta b/Assets/Scripts/GameManager.cs.meta
new file mode 100644
index 00000000..a6282ee4
--- /dev/null
+++ b/Assets/Scripts/GameManager.cs.meta
@@ -0,0 +1,2 @@
+fileFormatVersion: 2
+guid: 7bde02fc6ca2ab0468bb3ce777206089
\ No newline at end of file