diff --git a/src/app.ts b/src/app.ts
index 6406f9b110e..bdfad0e7b68 100644
--- a/src/app.ts
+++ b/src/app.ts
@@ -21,10 +21,12 @@ import { renderToString } from "preact-render-to-string";
 import { FinishSetup, ForgotBuild } from "./finish_setup.tsx";
 import { HttpError } from "./error.ts";
 
-const DEFAULT_NOT_FOUND = () =>
-  Promise.resolve(new Response("Not found", { status: 404 }));
-const DEFAULT_NOT_ALLOWED_METHOD = () =>
-  Promise.resolve(new Response("Method not allowed", { status: 405 }));
+const DEFAULT_NOT_FOUND = () => {
+  throw new HttpError(404);
+};
+const DEFAULT_NOT_ALLOWED_METHOD = () => {
+  throw new HttpError(405);
+};
 
 export type ListenOptions = Partial<Deno.ServeTlsOptions> & {
   remoteAddress?: string;
@@ -163,39 +165,6 @@ export class App<State> {
     return this;
   }
 
-  async #process(
-    req: Request,
-    params: Record<string, string>,
-    handlers: MiddlewareFn<State>[][],
-    next: () => Promise<Response>,
-  ) {
-    const ctx = new FreshReqContext<State>(
-      req,
-      this.config,
-      next,
-      this.#islandRegistry,
-      this.#buildCache!,
-    );
-
-    ctx.params = params;
-
-    try {
-      if (handlers.length === 1 && handlers[0].length === 1) {
-        return handlers[0][0](ctx);
-      }
-
-      ctx.next = next;
-      return await runMiddlewares(handlers, ctx);
-    } catch (err) {
-      if (err instanceof HttpError) {
-        return new Response(null, { status: err.status });
-      }
-
-      console.error(err);
-      return new Response("Internal server error", { status: 500 });
-    }
-  }
-
   async handler(): Promise<
     (request: Request, info?: Deno.ServeHandlerInfo) => Promise<Response>
   > {
@@ -207,7 +176,7 @@ export class App<State> {
       return missingBuildHandler;
     }
 
-    return (req: Request) => {
+    return async (req: Request) => {
       const url = new URL(req.url);
       // Prevent open redirect attacks
       url.pathname = url.pathname.replace(/\/+/g, "/");
@@ -215,16 +184,36 @@ export class App<State> {
       const method = req.method.toUpperCase() as Method;
       const matched = this.#router.match(method, url);
 
-      const fallback = matched.patternMatch && !matched.methodMatch
+      const next = matched.patternMatch && !matched.methodMatch
         ? DEFAULT_NOT_ALLOWED_METHOD
         : DEFAULT_NOT_FOUND;
 
-      return this.#process(
+      const { params, handlers } = matched;
+      const ctx = new FreshReqContext<State>(
         req,
-        matched.params,
-        matched.handlers,
-        fallback,
+        this.config,
+        next,
+        this.#islandRegistry,
+        this.#buildCache!,
       );
+
+      ctx.params = params;
+
+      try {
+        if (handlers.length === 1 && handlers[0].length === 1) {
+          return handlers[0][0](ctx);
+        }
+
+        ctx.next = next;
+        return await runMiddlewares(handlers, ctx);
+      } catch (err) {
+        if (err instanceof HttpError) {
+          return new Response(err.message, { status: err.status });
+        }
+
+        console.error(err);
+        return new Response("Internal server error", { status: 500 });
+      }
     };
   }
 
diff --git a/src/app_test.tsx b/src/app_test.tsx
index 72a9561b3d2..c9d9d1566ce 100644
--- a/src/app_test.tsx
+++ b/src/app_test.tsx
@@ -212,7 +212,7 @@ Deno.test("FreshApp - wrong method match", async () => {
 
   let res = await server.put("/");
   expect(res.status).toEqual(405);
-  expect(await res.text()).toEqual("Method not allowed");
+  expect(await res.text()).toEqual("Method Not Allowed");
 
   res = await server.post("/");
   expect(res.status).toEqual(200);
diff --git a/src/error.ts b/src/error.ts
index 365a4a63da3..e6e2c149531 100644
--- a/src/error.ts
+++ b/src/error.ts
@@ -1,13 +1,149 @@
 import { MODE } from "./runtime/server/mod.tsx";
 
+export function getMessage(status: number): string {
+  switch (status) {
+    case 100:
+      return "Continue";
+    case 101:
+      return "Switching Protocols";
+    case 102:
+      return "Processing (WebDAV)";
+    case 103:
+      return "Early Hints";
+    case 200:
+      return "OK";
+    case 201:
+      return "Created";
+    case 202:
+      return "Accepted";
+    case 203:
+      return "Non-Authoritative Information";
+    case 204:
+      return "No Content";
+    case 205:
+      return "Reset Content";
+    case 206:
+      return "Partial Content";
+    case 207:
+      return "Multi-Status (WebDAV)";
+    case 208:
+      return "Already Reported (WebDAV)";
+    case 226:
+      return "IM Used (HTTP Delta encoding)";
+    case 300:
+      return "Multiple Choices";
+    case 301:
+      return "Moved Permanently";
+    case 302:
+      return "Found";
+    case 303:
+      return "See Other";
+    case 304:
+      return "Not Modified";
+    case 305:
+      return "Use Proxy Deprecated";
+    case 306:
+      return "unused";
+    case 307:
+      return "Temporary Redirect";
+    case 308:
+      return "Permanent Redirect";
+    case 400:
+      return "Bad Request";
+    case 401:
+      return "Unauthorized";
+    case 402:
+      return "Payment Required Experimental";
+    case 403:
+      return "Forbidden";
+    case 404:
+      return "Not Found";
+    case 405:
+      return "Method Not Allowed";
+    case 406:
+      return "Not Acceptable";
+    case 407:
+      return "Proxy Authentication Required";
+    case 408:
+      return "Request Timeout";
+    case 409:
+      return "Conflict";
+    case 410:
+      return "Gone";
+    case 411:
+      return "Length Required";
+    case 412:
+      return "Precondition Failed";
+    case 413:
+      return "Payload Too Large";
+    case 414:
+      return "URI Too Long";
+    case 415:
+      return "Unsupported Media Type";
+    case 416:
+      return "Range Not Satisfiable";
+    case 417:
+      return "Expectation Failed";
+    case 418:
+      return "I'm a teapot";
+    case 421:
+      return "Misdirected Request";
+    case 422:
+      return "Unprocessable Content (WebDAV)";
+    case 423:
+      return "Locked (WebDAV)";
+    case 424:
+      return "Failed Dependency (WebDAV)";
+    case 425:
+      return "Too Early Experimental";
+    case 426:
+      return "Upgrade Required";
+    case 428:
+      return "Precondition Required";
+    case 429:
+      return "Too Many Requests";
+    case 431:
+      return "Request Header Fields Too Large";
+    case 451:
+      return "Unavailable For Legal Reasons";
+    case 500:
+      return "Internal Server Error";
+    case 501:
+      return "Not Implemented";
+    case 502:
+      return "Bad Gateway";
+    case 503:
+      return "Service Unavailable";
+    case 504:
+      return "Gateway Timeout";
+    case 505:
+      return "HTTP Version Not Supported";
+    case 506:
+      return "Variant Also Negotiates";
+    case 507:
+      return "Insufficient Storage (WebDAV)";
+    case 508:
+      return "Loop Detected (WebDAV)";
+    case 510:
+      return "Not Extended";
+    case 511:
+      return "Network Authentication Required";
+    default:
+      return "Internal Server Error";
+  }
+}
+
 export class HttpError {
   #error: Error | null = null;
   name = "HttpError";
+  message: string;
 
   constructor(
     public status: number,
+    message: string = getMessage(status),
     public options?: ErrorOptions,
   ) {
+    this.message = message;
     if (MODE !== "production") {
       this.#error = new Error();
     }
diff --git a/src/plugins/fs_routes/mod.ts b/src/plugins/fs_routes/mod.ts
index fecddef2a57..45d6fb9aafd 100644
--- a/src/plugins/fs_routes/mod.ts
+++ b/src/plugins/fs_routes/mod.ts
@@ -14,6 +14,7 @@ import { type Method, pathToPattern } from "../../router.ts";
 import { type HandlerFn, isHandlerByMethod } from "../../handlers.ts";
 import { type FsAdapter, fsAdapter } from "../../fs.ts";
 import type { PageProps } from "../../runtime/server/mod.tsx";
+import { HttpError } from "../../error.ts";
 
 const TEST_FILE_PATTERN = /[._]test\.(?:[tj]sx?|[mc][tj]s)$/;
 const GROUP_REG = /(^|[/\\\\])\((_[^/\\\\]+)\)[/\\\\]/;
@@ -183,6 +184,12 @@ export async function fsRoutes<State>(
     } else if (normalized.endsWith("/_error")) {
       stack.push(routeMod);
       continue;
+    } else if (normalized.endsWith("/_404")) {
+      stack.push(routeMod);
+      continue;
+    } else if (normalized.endsWith("/_500")) {
+      stack.push(routeMod);
+      continue;
     }
 
     // Remove any elements not matching our parent path anymore
@@ -227,7 +234,7 @@ export async function fsRoutes<State>(
         }
       }
 
-      if (mod.path.endsWith("/_error")) {
+      if (mod.path.endsWith("/_error") || mod.path.endsWith("/_500")) {
         const handlers = mod.handlers;
         const handler = handlers === null ||
             (isHandlerByMethod(handlers) && Object.keys(handlers).length === 0)
@@ -243,6 +250,22 @@ export async function fsRoutes<State>(
         continue;
       }
 
+      if (mod.path.endsWith("/_404")) {
+        const handlers = mod.handlers;
+        const handler = handlers === null ||
+            (isHandlerByMethod(handlers) && Object.keys(handlers).length === 0)
+          ? undefined
+          : typeof handlers === "function"
+          ? handlers
+          : undefined; // FIXME: Method handler
+        const notFoundComponents = components.slice();
+        if (mod.component !== null) {
+          notFoundComponents.push(mod.component);
+        }
+        app.use(notFoundMiddleware(notFoundComponents, handler));
+        continue;
+      }
+
       if (mod.component !== null) {
         components.push(mod.component);
       }
@@ -298,6 +321,23 @@ function errorMiddleware<State>(
   };
 }
 
+function notFoundMiddleware<State>(
+  components: AnyComponent<PageProps<unknown, State>>[],
+  handler: HandlerFn<unknown, State> | undefined,
+): MiddlewareFn<State> {
+  const mid = renderMiddleware<State>(components, handler);
+  return async function notFoundMiddleware(ctx) {
+    try {
+      return await ctx.next();
+    } catch (err) {
+      if (err instanceof HttpError && err.status === 404) {
+        return mid(ctx);
+      }
+      throw err;
+    }
+  };
+}
+
 async function walkDir(
   dir: string,
   callback: (entry: WalkEntry) => void,
diff --git a/src/plugins/fs_routes/mod_test.tsx b/src/plugins/fs_routes/mod_test.tsx
index ffe461c6aa1..22537bed8c4 100644
--- a/src/plugins/fs_routes/mod_test.tsx
+++ b/src/plugins/fs_routes/mod_test.tsx
@@ -542,11 +542,49 @@ Deno.test("fsRoutes - route overrides _app", async () => {
   expect(doc.body.firstChild?.textContent).toEqual("route");
 });
 
+Deno.test("fsRoutes - _404", async () => {
+  const server = await createServer({
+    "routes/_404.tsx": {
+      default: () => {
+        return <div>Custom 404 - Not Found</div>;
+      },
+    },
+    "routes/index.tsx": {
+      handlers: () => {
+        throw new Error("ok");
+      },
+    },
+  });
+
+  const res = await server.get("/invalid");
+  const content = await res.text();
+  expect(content).toContain("Custom 404 - Not Found");
+});
+
+Deno.test("fsRoutes - _500", async () => {
+  const server = await createServer({
+    "routes/_500.tsx": {
+      default: () => {
+        return <div>Custom Error Page</div>;
+      },
+    },
+    "routes/index.tsx": {
+      handlers: () => {
+        throw new Error("ok");
+      },
+    },
+  });
+
+  const res = await server.get("/");
+  const content = await res.text();
+  expect(content).toContain("Custom Error Page");
+});
+
 Deno.test("fsRoutes - _error", async () => {
   const server = await createServer({
     "routes/_error.tsx": {
-      default: (ctx) => {
-        return <div>{(ctx.error as Error).message}</div>;
+      default: () => {
+        return <div>Custom Error Page</div>;
       },
     },
     "routes/index.tsx": {
@@ -557,8 +595,8 @@ Deno.test("fsRoutes - _error", async () => {
   });
 
   const res = await server.get("/");
-  const doc = parseHtml(await res.text());
-  expect(doc.body.firstChild?.textContent).toEqual("ok");
+  const content = await res.text();
+  expect(content).toContain("Custom Error Page");
 });
 
 Deno.test("fsRoutes - _error nested", async () => {