diff --git a/Foxnouns.Backend/Controllers/SidController.cs b/Foxnouns.Backend/Controllers/SidController.cs
index 26c66ef..b8f5948 100644
--- a/Foxnouns.Backend/Controllers/SidController.cs
+++ b/Foxnouns.Backend/Controllers/SidController.cs
@@ -1,3 +1,52 @@
+using System.Diagnostics.CodeAnalysis;
+using Foxnouns.Backend.Database;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+
 namespace Foxnouns.Backend.Controllers;
 
-public class SidController { }
+[Route("/sid")]
+[SuppressMessage(
+    "Performance",
+    "CA1862:Use the \'StringComparison\' method overloads to perform case-insensitive string comparisons",
+    Justification = "Not usable with EFCore"
+)]
+public class SidController(Config config, DatabaseContext db) : ApiControllerBase
+{
+    [HttpGet("{**id}")]
+    public async Task<IActionResult> ResolveSidAsync(string id, CancellationToken ct = default) =>
+        id.Length switch
+        {
+            5 => await ResolveUserSidAsync(id, ct),
+            6 => await ResolveMemberSidAsync(id, ct),
+            _ => Redirect(config.BaseUrl),
+        };
+
+    private async Task<IActionResult> ResolveUserSidAsync(string id, CancellationToken ct = default)
+    {
+        var username = await db
+            .Users.Where(u => u.Sid == id.ToLowerInvariant() && !u.Deleted)
+            .Select(u => u.Username)
+            .FirstOrDefaultAsync(ct);
+        if (username == null)
+            return Redirect(config.BaseUrl);
+
+        return Redirect($"{config.BaseUrl}/@{username}");
+    }
+
+    private async Task<IActionResult> ResolveMemberSidAsync(
+        string id,
+        CancellationToken ct = default
+    )
+    {
+        var member = await db
+            .Members.Include(m => m.User)
+            .Where(m => m.Sid == id.ToLowerInvariant() && !m.User.Deleted)
+            .Select(m => new { m.Name, m.User.Username })
+            .FirstOrDefaultAsync(ct);
+        if (member == null)
+            return Redirect(config.BaseUrl);
+
+        return Redirect($"{config.BaseUrl}/@{member.Username}/{member.Name}");
+    }
+}