diff --git a/DysonNetwork.Sphere/AppDatabase.cs b/DysonNetwork.Sphere/AppDatabase.cs
index 9d977fb..6079f64 100644
--- a/DysonNetwork.Sphere/AppDatabase.cs
+++ b/DysonNetwork.Sphere/AppDatabase.cs
@@ -50,6 +50,9 @@ public class AppDatabase(
 
     public DbSet<Realm.Realm> Realms { get; set; }
     public DbSet<Realm.RealmMember> RealmMembers { get; set; }
+    
+    public DbSet<Chat.ChatRoom> ChatRooms { get; set; }
+    public DbSet<Chat.ChatMember> ChatMembers { get; set; }
 
     protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
     {
@@ -165,7 +168,20 @@ public class AppDatabase(
             .WithMany(p => p.Members)
             .HasForeignKey(pm => pm.RealmId)
             .OnDelete(DeleteBehavior.Cascade);
-        modelBuilder.Entity<Post.PublisherMember>()
+        modelBuilder.Entity<Realm.RealmMember>()
+            .HasOne(pm => pm.Account)
+            .WithMany()
+            .HasForeignKey(pm => pm.AccountId)
+            .OnDelete(DeleteBehavior.Cascade);
+        
+        modelBuilder.Entity<Chat.ChatMember>()
+            .HasKey(pm => new { pm.ChatRoom, pm.AccountId });
+        modelBuilder.Entity<Chat.ChatMember>()
+            .HasOne(pm => pm.ChatRoom)
+            .WithMany(p => p.Members)
+            .HasForeignKey(pm => pm.ChatRoomId)
+            .OnDelete(DeleteBehavior.Cascade);
+        modelBuilder.Entity<Chat.ChatMember>()
             .HasOne(pm => pm.Account)
             .WithMany()
             .HasForeignKey(pm => pm.AccountId)
diff --git a/DysonNetwork.Sphere/Chat/ChatController.cs b/DysonNetwork.Sphere/Chat/ChatController.cs
new file mode 100644
index 0000000..0be8635
--- /dev/null
+++ b/DysonNetwork.Sphere/Chat/ChatController.cs
@@ -0,0 +1,15 @@
+using DysonNetwork.Sphere.Account;
+using DysonNetwork.Sphere.Realm;
+using DysonNetwork.Sphere.Chat;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using System.Threading.Tasks;
+
+namespace DysonNetwork.Sphere.Chat;
+
+[ApiController]
+[Route("/chat")]
+public class ChatController(AppDatabase db) : ControllerBase
+{
+}
\ No newline at end of file
diff --git a/DysonNetwork.Sphere/Chat/ChatRoom.cs b/DysonNetwork.Sphere/Chat/ChatRoom.cs
new file mode 100644
index 0000000..35540bb
--- /dev/null
+++ b/DysonNetwork.Sphere/Chat/ChatRoom.cs
@@ -0,0 +1,48 @@
+using System.ComponentModel.DataAnnotations;
+using System.Text.Json.Serialization;
+using DysonNetwork.Sphere.Storage;
+using NodaTime;
+
+namespace DysonNetwork.Sphere.Chat;
+
+public enum ChatRoomType
+{
+    Group,
+    DirectMessage
+}
+
+public class ChatRoom : ModelBase
+{
+    public long Id { get; set; }
+    [MaxLength(1024)] public string Name { get; set; } = string.Empty;
+    [MaxLength(4096)] public string Description { get; set; } = string.Empty;
+    public ChatRoomType Type { get; set; }
+    public bool IsPublic { get; set; }
+
+    public CloudFile? Picture { get; set; }
+    public CloudFile? Background { get; set; }
+
+    [JsonIgnore] public ICollection<ChatMember> Members { get; set; } = new List<ChatMember>();
+
+    public long? RealmId { get; set; }
+    public Realm.Realm? Realm { get; set; }
+}
+
+public enum ChatMemberRole
+{
+    Owner = 100,
+    Moderator = 50,
+    Normal = 0
+}
+
+public class ChatMember : ModelBase
+{
+    public long ChatRoomId { get; set; }
+    [JsonIgnore] public ChatRoom ChatRoom { get; set; } = null!;
+    public long AccountId { get; set; }
+    [JsonIgnore] public Account.Account Account { get; set; } = null!;
+
+    public ChatMemberRole Role { get; set; }
+    public Instant? JoinedAt { get; set; }
+    public bool IsBot { get; set; } = false;
+}
\ No newline at end of file
diff --git a/DysonNetwork.Sphere/Realm/Realm.cs b/DysonNetwork.Sphere/Realm/Realm.cs
index 7e3995d..602cc30 100644
--- a/DysonNetwork.Sphere/Realm/Realm.cs
+++ b/DysonNetwork.Sphere/Realm/Realm.cs
@@ -1,5 +1,6 @@
 using System.ComponentModel.DataAnnotations;
 using System.Text.Json.Serialization;
+using DysonNetwork.Sphere.Chat;
 using DysonNetwork.Sphere.Storage;
 using Microsoft.EntityFrameworkCore;
 using NodaTime;
@@ -22,9 +23,10 @@ public class Realm : ModelBase
     public CloudFile? Background { get; set; }
     
     [JsonIgnore] public ICollection<RealmMember> Members { get; set; } = new List<RealmMember>();
+    [JsonIgnore] public ICollection<ChatRoom> ChatRooms { get; set; } = new List<ChatRoom>();
 
     public long AccountId { get; set; }
-    [JsonIgnore] public Account.Account Account { get; set; }
+    [JsonIgnore] public Account.Account Account { get; set; } = null!;
 }
 
 public enum RealmMemberRole