diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Context/IdentityContext.cs b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Context/IdentityContext.cs
index 2455d74b9..41568d692 100644
--- a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Context/IdentityContext.cs
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Context/IdentityContext.cs
@@ -44,8 +44,13 @@ public IdentityContext(HttpContext httpContext)
 
     public IdentityContext(ClaimsPrincipal principal)
     {
-        _IdentityUserId = principal.FindFirst(ClaimTypes.NameIdentifier) is var idClaim && idClaim is not null
-            ? new Guid(idClaim.Value) : null;
+        if(principal.Identity!.AuthenticationType != "GitHub" 
+            && principal.FindFirst(ClaimTypes.NameIdentifier) is var idClaim
+            && idClaim is not null)
+        {
+            _IdentityUserId = Guid.Parse(idClaim.Value);
+        }
+            
         Name = principal.FindFirst(ClaimTypes.Name)?.Value;
         IsAdmin = principal.FindAll(ClaimTypes.Role).Any(x => x.Value == Role.Admin);
         IsContentEditor = principal.FindAll(ClaimTypes.Role).Any(x => x.Value == Role.ContentEditor) && !IsAdmin;
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Controllers/GithubAuthenticationController.cs b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Controllers/GithubAuthenticationController.cs
new file mode 100644
index 000000000..d4fcf9c6a
--- /dev/null
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Controllers/GithubAuthenticationController.cs
@@ -0,0 +1,49 @@
+using GreenOnSoftware.Application.GithubAuthentication;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+namespace GreenOnSoftware.Api.Controllers;
+
+[Route("api/[controller]")]
+[ApiController]
+public class GithubAuthenticationController : ControllerBase
+{
+    private readonly IGithubAuthenticationService _githubAuthenticationService;
+
+    public GithubAuthenticationController(IGithubAuthenticationService githubAuthenticationService)
+    {
+        _githubAuthenticationService = githubAuthenticationService;
+    }
+
+    [HttpGet("[action]")]
+    public IActionResult SignIn(string? redirectUrl)
+    {
+        if (!string.IsNullOrEmpty(redirectUrl))
+        {
+            HttpContext.Session.SetString("GithubAuthorization:RedirectUrl", redirectUrl);
+        }
+        var properties = _githubAuthenticationService.CreateAuthenticationProperties("/api/GithubAuthentication/Authenticate");
+
+        return Challenge(properties, "GitHub");
+    }
+
+    [Authorize(AuthenticationSchemes = "Identity.Application, Identity.External")]
+    [HttpGet("[Action]")]
+    public async Task<IActionResult> Authenticate()
+    {
+        var result = await _githubAuthenticationService.AuthenticateAsync();
+        if (result.HasErrors)
+        {
+            return BadRequest(result);
+        }
+        string? redirectUrl = HttpContext.Session.GetString("GithubAuthorization:RedirectUrl");
+        if (string.IsNullOrEmpty(redirectUrl))
+        {
+            return Ok(result);
+        }
+
+        HttpContext.Session.Remove("GithubAuthorization:RedirectUrl");
+
+        return Redirect(redirectUrl);
+    }
+}
\ No newline at end of file
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/GreenOnSoftware.Api.csproj b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/GreenOnSoftware.Api.csproj
index a383f0f6b..a53450acc 100644
--- a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/GreenOnSoftware.Api.csproj
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/GreenOnSoftware.Api.csproj
@@ -19,6 +19,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="AspNet.Security.OAuth.GitHub" Version="6.0.15" />
     <PackageReference Include="AutoMapper" Version="11.0.1" />
     <PackageReference Include="AutoMapper.Extensions.Microsoft.DependencyInjection" Version="11.0.0" />
     <PackageReference Include="FluentValidation.AspNetCore" Version="11.1.2" />
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Program.cs b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Program.cs
index ec42ea718..ad69e8750 100644
--- a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Program.cs
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Program.cs
@@ -41,7 +41,7 @@
 builder.Services.AddDbContext<GreenOnSoftwareDbContext>(options =>
   options.UseSqlServer(builder.Configuration.GetConnectionString("GreenOnSoftware")));
 
-builder.Services.AddIdentity();
+builder.Services.AddAuthentication(builder.Configuration);
 
 builder.Services.AddCors();
 
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Startup/IdentityConfig.cs b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Startup/AuthenticationConfig.cs
similarity index 74%
rename from dotnet/GreenOnSoftware/GreenOnSoftware.Api/Startup/IdentityConfig.cs
rename to dotnet/GreenOnSoftware/GreenOnSoftware.Api/Startup/AuthenticationConfig.cs
index 3fe009ba6..4f0697e4c 100644
--- a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Startup/IdentityConfig.cs
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/Startup/AuthenticationConfig.cs
@@ -5,9 +5,9 @@
 
 namespace GreenOnSoftware.Api.Startup;
 
-public static class IdentityConfig
+public static class AuthenticationConfig
 {
-    public static IServiceCollection AddIdentity(this IServiceCollection services)
+    public static IServiceCollection AddAuthentication(this IServiceCollection services, IConfiguration configuration)
     {
         services.AddIdentity<User, IdentityRole<Guid>>(options => options.SignIn.RequireConfirmedAccount = false)
             .AddEntityFrameworkStores<GreenOnSoftwareDbContext>()
@@ -53,6 +53,22 @@ public static IServiceCollection AddIdentity(this IServiceCollection services)
             };
         });
 
+        var githubConfig = configuration.GetSection("Github");
+
+        var siema = githubConfig["ClientSecret"];
+
+        services
+            .AddAuthentication(options =>
+            {
+                options.DefaultChallengeScheme = IdentityConstants.ExternalScheme;
+            })
+            .AddGitHub(options => {
+                options.ClientId = githubConfig["ClientId"];
+                options.ClientSecret = githubConfig["ClientSecret"];
+                options.Scope.Add("user:email");
+                options.SaveTokens = true;
+            });
+
         return services;
     }
 }
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/appsettings.Development.json b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/appsettings.Development.json
index e3eb29545..63ed782c5 100644
--- a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/appsettings.Development.json
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/appsettings.Development.json
@@ -21,5 +21,10 @@
   "BlobStorage": {
     "ConnectionString": "--secret--",
     "Container": "dev"
+  },
+
+  "Github": {
+    "ClientId": "In secrets.json",
+    "ClientSecret": "In secrets.json"
   }
 }
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/appsettings.dev.json b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/appsettings.dev.json
index bd4ff71a3..e312326d9 100644
--- a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/appsettings.dev.json
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/appsettings.dev.json
@@ -22,5 +22,10 @@
   "BlobStorage": {
     "ConnectionString": "--secret--",
     "Container": "dev"
+  },
+
+  "Github": {
+    "ClientId": "In secrets.json",
+    "ClientSecret": "In secrets.json"
   }
 }
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/appsettings.prod.json b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/appsettings.prod.json
index 147b01251..e0439e808 100644
--- a/dotnet/GreenOnSoftware/GreenOnSoftware.Api/appsettings.prod.json
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Api/appsettings.prod.json
@@ -26,5 +26,10 @@
 
   "CorsOriginsUrls": [
     "https://greenonsoftware.com"
-  ]
+  ],
+
+  "Github": {
+    "ClientId": "In secrets.json",
+    "ClientSecret": "In secrets.json"
+  }
 }
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Application/DependencyInjection.cs b/dotnet/GreenOnSoftware/GreenOnSoftware.Application/DependencyInjection.cs
index bf2d75031..49a17be8a 100644
--- a/dotnet/GreenOnSoftware/GreenOnSoftware.Application/DependencyInjection.cs
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Application/DependencyInjection.cs
@@ -1,4 +1,5 @@
-using GreenOnSoftware.Application.Services;
+using GreenOnSoftware.Application.GithubAuthentication;
+using GreenOnSoftware.Application.Services;
 using GreenOnSoftware.Application.Services.Interfaces;
 using Microsoft.Extensions.DependencyInjection;
 
@@ -13,6 +14,7 @@ public static IServiceCollection AddApplication(this IServiceCollection services
         services.AddTransient<IRatingsSessionService, RatingsSessionService>();
         services.AddTransient<IArticleUrlIdentifierService, ArticleUrlIdentifierService>();
         services.AddTransient<ITagsService, TagsService>();
+        services.AddTransient<IGithubAuthenticationService, GithubAuthenticationService>();
 
         return services;
     }
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Application/GithubAuthentication/GithubAuthenticationService.cs b/dotnet/GreenOnSoftware/GreenOnSoftware.Application/GithubAuthentication/GithubAuthenticationService.cs
new file mode 100644
index 000000000..a652b2140
--- /dev/null
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Application/GithubAuthentication/GithubAuthenticationService.cs
@@ -0,0 +1,148 @@
+using GreenOnSoftware.Commons.Dtos;
+using GreenOnSoftware.Commons.Resources;
+using GreenOnSoftware.Core.Identity;
+using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Identity;
+using Serilog;
+using System.Security.Claims;
+using GreenOnSoftware.Commons.Extensions;
+using GreenOnSoftware.Commons.Consts;
+
+namespace GreenOnSoftware.Application.GithubAuthentication;
+
+public class GithubAuthenticationService : IGithubAuthenticationService
+{
+    private readonly UserManager<User> _userManager;
+    private readonly SignInManager<User> _signInManager;
+
+    public GithubAuthenticationService(
+        UserManager<User> userManager,
+        SignInManager<User> signInManager)
+    {
+        _userManager = userManager;
+        _signInManager = signInManager;
+    }
+
+    public AuthenticationProperties CreateAuthenticationProperties(string redirectUrl)
+    {
+
+        return _signInManager.ConfigureExternalAuthenticationProperties("GitHub", new PathString(redirectUrl));
+    }
+
+    public async Task<Result<GithubTokenDto>> AuthenticateAsync()
+    {
+        var response = new Result<GithubTokenDto>();
+
+        var externalLoginInfo = await _signInManager.GetExternalLoginInfoAsync();
+        if (externalLoginInfo is null)
+        {
+            response.AddError(ErrorMessages.ActionFailed, ErrorActionNames.ExternalSignIn);
+            return response;
+        }
+        string? applicationUserId = GetAppicationUserId();
+
+        var user = await _userManager.FindByLoginAsync(externalLoginInfo.LoginProvider, externalLoginInfo.ProviderKey);
+        if (user is null)
+        {
+            var userResult = await GetApplicationUser(applicationUserId, externalLoginInfo.Principal.Claims);
+            if (userResult.HasErrors)
+            {
+                response.AddErrors(userResult);
+                response.AddError(ErrorMessages.ActionFailed, ErrorActionNames.ExternalSignIn);
+                return response;
+            }
+            user = userResult.Data;
+
+            var addLoginResult = await _userManager.AddLoginAsync(user, externalLoginInfo);
+            if (!addLoginResult.Succeeded)
+            {
+                response.AddError(ErrorMessages.ActionFailed, ErrorActionNames.AddExternalLogin);
+                return response;
+            }
+        }
+        else
+        {
+            if (!string.IsNullOrEmpty(applicationUserId) && applicationUserId != user.Id.ToString())
+            {
+                response.AddError(ErrorMessages.AlreadyConnectedWithAnotherAccount);
+                return response;
+            }
+        }
+
+        SignInResult signInResult = await _signInManager.ExternalLoginSignInAsync(externalLoginInfo.LoginProvider, externalLoginInfo.ProviderKey, true);
+
+        if (!signInResult.Succeeded)
+        {
+            response.AddError(ErrorMessages.ActionFailed, ErrorActionNames.ExternalSignIn);
+            return response;
+        }
+
+        IdentityResult saveTokensResult = await _signInManager.UpdateExternalAuthenticationTokensAsync(externalLoginInfo);
+
+        if (!saveTokensResult.Succeeded)
+        {
+            response.AddErrors(saveTokensResult.GetErrors());
+            return response;
+        }
+
+        return response;
+    }
+
+    public async Task<string> GetGithubTokenAsync(string username = null)
+    {
+        if (string.IsNullOrEmpty(username))
+        {
+            username = _signInManager.Context.User.Claims.Single(x => x.Type == ClaimTypes.Name).Value;
+        }
+
+        User currentUser = await _userManager.FindByNameAsync(username);
+        string githubToken = await _userManager.GetAuthenticationTokenAsync(currentUser, "Github", "access_token");
+
+        return githubToken;
+    }
+
+    private string? GetAppicationUserId()
+    {
+        return _signInManager.Context.User
+            .Identities
+            .SingleOrDefault(x => x.AuthenticationType == IdentityConstants.ApplicationScheme)
+            ?.Claims
+            .Single(x => x.Type == ClaimTypes.NameIdentifier)
+            .Value;
+    }
+
+    private async Task<Result<User>> GetApplicationUser(string? applicationUserId, IEnumerable<Claim> externalClaims)
+    {
+        var result = new Result<User>();
+        if (applicationUserId != null)
+        {
+            result.SetData(await _userManager.FindByIdAsync(applicationUserId));
+            if (result.Data != null)
+            {
+                return result;
+            }
+        }
+
+        var newUser = new User {
+            Email = externalClaims.Single(x => x.Type == ClaimTypes.Email).Value,
+            UserName = externalClaims.Single(x => x.Type == ClaimTypes.Name).Value,
+        };
+        var addUserResult = await _userManager.CreateAsync(newUser);
+        if (!addUserResult.Succeeded)
+        {
+            result.AddErrors(addUserResult.GetErrors());
+            return result;
+        }
+        var addToRoleResult = await _userManager.AddToRoleAsync(newUser, Role.GeneralUser);
+        if (!addToRoleResult.Succeeded)
+        {
+            result.AddErrors(addToRoleResult.GetErrors());
+            Log.Error($"Failed to assign role to new user {newUser.UserName}.");
+        }
+
+        result.SetData(newUser);
+
+        return result;
+    }
+}
\ No newline at end of file
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Application/GithubAuthentication/GithubTokenDto.cs b/dotnet/GreenOnSoftware/GreenOnSoftware.Application/GithubAuthentication/GithubTokenDto.cs
new file mode 100644
index 000000000..664d72c67
--- /dev/null
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Application/GithubAuthentication/GithubTokenDto.cs
@@ -0,0 +1,7 @@
+namespace GreenOnSoftware.Application.GithubAuthentication;
+
+public class GithubTokenDto
+{
+    public string AccessToken { get; set; }
+    public IEnumerable<string> Scope { get; set; }
+}
\ No newline at end of file
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Application/GithubAuthentication/IGithubAuthenticationService.cs b/dotnet/GreenOnSoftware/GreenOnSoftware.Application/GithubAuthentication/IGithubAuthenticationService.cs
new file mode 100644
index 000000000..a197b62dc
--- /dev/null
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Application/GithubAuthentication/IGithubAuthenticationService.cs
@@ -0,0 +1,11 @@
+using GreenOnSoftware.Commons.Dtos;
+using Microsoft.AspNetCore.Authentication;
+
+namespace GreenOnSoftware.Application.GithubAuthentication;
+
+public interface IGithubAuthenticationService
+{
+    Task<Result<GithubTokenDto>> AuthenticateAsync();
+    AuthenticationProperties CreateAuthenticationProperties(string redirectUrl);
+    Task<string> GetGithubTokenAsync(string? username = null);
+}
\ No newline at end of file
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Application/_Services/ThumbnailService.cs b/dotnet/GreenOnSoftware/GreenOnSoftware.Application/_Services/ThumbnailService.cs
index add2e548b..6d2fe5bf1 100644
--- a/dotnet/GreenOnSoftware/GreenOnSoftware.Application/_Services/ThumbnailService.cs
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Application/_Services/ThumbnailService.cs
@@ -1,4 +1,5 @@
-using GreenOnSoftware.Application.Services.Interfaces;
+using GreenOnSoftware.Application.Account.SignInCommand;
+using GreenOnSoftware.Application.Services.Interfaces;
 using GreenOnSoftware.Commons.Dtos;
 using GreenOnSoftware.Commons.Resources;
 using Microsoft.AspNetCore.Http;
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Commons/Consts/ErrorActionNames.cs b/dotnet/GreenOnSoftware/GreenOnSoftware.Commons/Consts/ErrorActionNames.cs
new file mode 100644
index 000000000..f36a7f796
--- /dev/null
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Commons/Consts/ErrorActionNames.cs
@@ -0,0 +1,9 @@
+namespace GreenOnSoftware.Commons.Consts;
+
+public static class ErrorActionNames
+{
+    public const string AddExternalLogin = "Add external login";
+    public const string EmailConfirmation = "Email confirmation";
+    public const string EmailSending = "Email sending";
+    public const string ExternalSignIn = "External sign in";
+}
\ No newline at end of file
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Commons/Resources/ErrorMessages.Designer.cs b/dotnet/GreenOnSoftware/GreenOnSoftware.Commons/Resources/ErrorMessages.Designer.cs
index 63ef22f2f..8b962db0f 100644
--- a/dotnet/GreenOnSoftware/GreenOnSoftware.Commons/Resources/ErrorMessages.Designer.cs
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Commons/Resources/ErrorMessages.Designer.cs
@@ -69,6 +69,15 @@ public static string ActionFailed {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to This github account is already connected with another user..
+        /// </summary>
+        public static string AlreadyConnectedWithAnotherAccount {
+            get {
+                return ResourceManager.GetString("AlreadyConnectedWithAnotherAccount", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Article already exists..
         /// </summary>
diff --git a/dotnet/GreenOnSoftware/GreenOnSoftware.Commons/Resources/ErrorMessages.resx b/dotnet/GreenOnSoftware/GreenOnSoftware.Commons/Resources/ErrorMessages.resx
index c5f29209f..8d1ca4a20 100644
--- a/dotnet/GreenOnSoftware/GreenOnSoftware.Commons/Resources/ErrorMessages.resx
+++ b/dotnet/GreenOnSoftware/GreenOnSoftware.Commons/Resources/ErrorMessages.resx
@@ -120,6 +120,9 @@
   <data name="ActionFailed" xml:space="preserve">
     <value>{0} failed.</value>
   </data>
+  <data name="AlreadyConnectedWithAnotherAccount" xml:space="preserve">
+    <value>This github account is already connected with another user.</value>
+  </data>
   <data name="ArticleAlreadyExists" xml:space="preserve">
     <value>Article already exists.</value>
   </data>