diff --git a/src/Services/Identity/Identity.Domain/DTOs/AppUserDto.cs b/src/Services/Identity/Identity.Domain/DTOs/AppUserDto.cs
new file mode 100644
index 0000000..55502ba
--- /dev/null
+++ b/src/Services/Identity/Identity.Domain/DTOs/AppUserDto.cs
@@ -0,0 +1,11 @@
+namespace Identity.Domain.DTOs;
+
+public class AppUserDto
+{
+    public Guid Id { get; set; }
+    public string UserName { get; set; } = string.Empty;
+    public string Email { get; set; } = string.Empty;
+    public string? FullName { get; set; }
+    public string? JobTitle { get; set; }
+    public bool IsEnabled { get; set; }
+}
diff --git a/src/Services/Identity/Identity.Domain/DTOs/LoginRequest.cs b/src/Services/Identity/Identity.Domain/DTOs/LoginRequest.cs
new file mode 100644
index 0000000..e700f79
--- /dev/null
+++ b/src/Services/Identity/Identity.Domain/DTOs/LoginRequest.cs
@@ -0,0 +1,7 @@
+namespace Identity.Domain.DTOs;
+
+public class LoginRequest
+{
+    public string UserName { get; set; } = string.Empty;
+    public string Password { get; set; } = string.Empty;
+}
diff --git a/src/Services/Identity/Identity.Domain/DTOs/LoginResult.cs b/src/Services/Identity/Identity.Domain/DTOs/LoginResult.cs
new file mode 100644
index 0000000..980e31d
--- /dev/null
+++ b/src/Services/Identity/Identity.Domain/DTOs/LoginResult.cs
@@ -0,0 +1,8 @@
+namespace Identity.Domain.DTOs;
+
+public class LoginResult
+{
+    public bool Success { get; set; }
+    public string? ErrorMessage { get; set; }
+    public string? Token { get; set; }
+}
diff --git a/src/Services/Identity/Identity.Domain/DTOs/RegisterRequest.cs b/src/Services/Identity/Identity.Domain/DTOs/RegisterRequest.cs
new file mode 100644
index 0000000..e0a66b9
--- /dev/null
+++ b/src/Services/Identity/Identity.Domain/DTOs/RegisterRequest.cs
@@ -0,0 +1,10 @@
+namespace Identity.Domain.DTOs;
+
+public class RegisterRequest
+{
+    public string UserName { get; set; } = string.Empty;
+    public string Email { get; set; } = string.Empty;
+    public string Password { get; set; } = string.Empty;
+    public string? FullName { get; set; }
+    public string? JobTitle { get; set; }
+}
diff --git a/src/Services/Identity/Identity.Domain/DTOs/RegisterResult.cs b/src/Services/Identity/Identity.Domain/DTOs/RegisterResult.cs
new file mode 100644
index 0000000..2449e40
--- /dev/null
+++ b/src/Services/Identity/Identity.Domain/DTOs/RegisterResult.cs
@@ -0,0 +1,8 @@
+namespace Identity.Domain.DTOs;
+
+public class RegisterResult
+{
+    public bool Success { get; set; }
+    public string? ErrorMessage { get; set; }
+    public AppUserDto? User { get; set; }
+}
diff --git a/src/Services/Identity/Identity.Domain/Entities/AppRole.cs b/src/Services/Identity/Identity.Domain/Entities/AppRole.cs
new file mode 100644
index 0000000..1d1f1df
--- /dev/null
+++ b/src/Services/Identity/Identity.Domain/Entities/AppRole.cs
@@ -0,0 +1,8 @@
+namespace Identity.Domain.Entities;
+
+public class AppRole
+{
+    public Guid Id { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public string? Description { get; set; }
+}
diff --git a/src/Services/Identity/Identity.Domain/Entities/AppUser.cs b/src/Services/Identity/Identity.Domain/Entities/AppUser.cs
new file mode 100644
index 0000000..4eaf7b2
--- /dev/null
+++ b/src/Services/Identity/Identity.Domain/Entities/AppUser.cs
@@ -0,0 +1,14 @@
+namespace Identity.Domain.Entities;
+
+public class AppUser
+{
+    public Guid Id { get; set; }
+    public string UserName { get; set; } = string.Empty;
+    public string Email { get; set; } = string.Empty;
+    public string PasswordHash { get; set; } = string.Empty;
+    public string? FullName { get; set; }
+    public string? JobTitle { get; set; }
+    public bool IsEnabled { get; set; } = true;
+    public DateTime CreatedAt { get; set; }
+    public DateTime UpdatedAt { get; set; }
+}
diff --git a/src/Services/Identity/Identity.Domain/Interfaces/IIdentityService.cs b/src/Services/Identity/Identity.Domain/Interfaces/IIdentityService.cs
new file mode 100644
index 0000000..4985edf
--- /dev/null
+++ b/src/Services/Identity/Identity.Domain/Interfaces/IIdentityService.cs
@@ -0,0 +1,11 @@
+using Identity.Domain.DTOs;
+
+namespace Identity.Domain.Interfaces;
+
+public interface IIdentityService
+{
+    Task<RegisterResult> RegisterAsync(RegisterRequest request);
+    Task<LoginResult> LoginAsync(LoginRequest request);
+    Task<AppUserDto?> GetUserByIdAsync(Guid id);
+    Task<IEnumerable<AppUserDto>> GetAllUsersAsync();
+}