diff --git a/packages/astro/src/core/errors/errors-data.ts b/packages/astro/src/core/errors/errors-data.ts
index 251063621967..d662a0f71845 100644
--- a/packages/astro/src/core/errors/errors-data.ts
+++ b/packages/astro/src/core/errors/errors-data.ts
@@ -995,6 +995,20 @@ export const RedirectWithNoLocation = {
 	name: 'RedirectWithNoLocation',
 	title: 'A redirect must be given a location with the `Location` header.',
 } satisfies ErrorData;
+
+/**
+ * @docs
+ * @see
+ * - [Astro.redirect](https://docs.astro.build/en/reference/api-reference/#redirect)
+ * @description
+ * An external redirect must start with http or https, and must be a valid URL
+ */
+export const UnsupportedExternalRedirect = {
+	name: 'UnsupportedExternalRedirect',
+	title: 'Unsupported or malformed URL.',
+	message: 'An external redirect must start with http or https, and must be a valid URL',
+} satisfies ErrorData;
+
 /**
  * @docs
  * @see
diff --git a/packages/astro/src/core/redirects/render.ts b/packages/astro/src/core/redirects/render.ts
index 379f26e3ba48..6245db9e0fd5 100644
--- a/packages/astro/src/core/redirects/render.ts
+++ b/packages/astro/src/core/redirects/render.ts
@@ -1,5 +1,14 @@
+import type { RedirectConfig } from '../../types/public/index.js';
 import type { RenderContext } from '../render-context.js';
 
+export function redirectIsExternal(redirect: RedirectConfig): boolean {
+	if (typeof redirect === 'string') {
+		return redirect.startsWith('http') || redirect.startsWith('https');
+	} else {
+		return redirect.destination.startsWith('http') || redirect.destination.startsWith('https');
+	}
+}
+
 export async function renderRedirect(renderContext: RenderContext) {
 	const {
 		request: { method },
@@ -9,6 +18,13 @@ export async function renderRedirect(renderContext: RenderContext) {
 	const status =
 		redirectRoute && typeof redirect === 'object' ? redirect.status : method === 'GET' ? 301 : 308;
 	const headers = { location: encodeURI(redirectRouteGenerate(renderContext)) };
+	if (redirect && redirectIsExternal(redirect)) {
+		if (typeof redirect === 'string') {
+			return Response.redirect(redirect, status);
+		} else {
+			return Response.redirect(redirect.destination, status);
+		}
+	}
 	return new Response(null, { status, headers });
 }
 
@@ -21,13 +37,17 @@ function redirectRouteGenerate(renderContext: RenderContext): string {
 	if (typeof redirectRoute !== 'undefined') {
 		return redirectRoute?.generate(params) || redirectRoute?.pathname || '/';
 	} else if (typeof redirect === 'string') {
-		// TODO: this logic is duplicated between here and manifest/create.ts
-		let target = redirect;
-		for (const param of Object.keys(params)) {
-			const paramValue = params[param]!;
-			target = target.replace(`[${param}]`, paramValue).replace(`[...${param}]`, paramValue);
+		if (redirectIsExternal(redirect)) {
+			return redirect;
+		} else {
+			// TODO: this logic is duplicated between here and manifest/create.ts
+			let target = redirect;
+			for (const param of Object.keys(params)) {
+				const paramValue = params[param]!;
+				target = target.replace(`[${param}]`, paramValue).replace(`[...${param}]`, paramValue);
+			}
+			return target;
 		}
-		return target;
 	} else if (typeof redirect === 'undefined') {
 		return '/';
 	}
diff --git a/packages/astro/src/core/routing/manifest/create.ts b/packages/astro/src/core/routing/manifest/create.ts
index b0495a682ad8..73c4229c25d6 100644
--- a/packages/astro/src/core/routing/manifest/create.ts
+++ b/packages/astro/src/core/routing/manifest/create.ts
@@ -14,7 +14,10 @@ import { getPrerenderDefault } from '../../../prerender/utils.js';
 import type { AstroConfig } from '../../../types/public/config.js';
 import type { RouteData, RoutePart } from '../../../types/public/internal.js';
 import { SUPPORTED_MARKDOWN_FILE_EXTENSIONS } from '../../constants.js';
-import { MissingIndexForInternationalization } from '../../errors/errors-data.js';
+import {
+	MissingIndexForInternationalization,
+	UnsupportedExternalRedirect,
+} from '../../errors/errors-data.js';
 import { AstroError } from '../../errors/index.js';
 import { removeLeadingForwardSlash, slash } from '../../path.js';
 import { injectServerIslandRoute } from '../../server-islands/endpoint.js';
@@ -348,11 +351,13 @@ function createRedirectRoutes(
 			destination = to.destination;
 		}
 
-		if (/^https?:\/\//.test(destination)) {
-			logger.warn(
-				'redirects',
-				`Redirecting to an external URL is not officially supported: ${from} -> ${destination}`,
-			);
+		// URLs that don't start with leading slash should be considered external
+		if (!destination.startsWith('/')) {
+			// check if the link starts with http or https; if not, log a warning
+			if (!/^https?:\/\//.test(destination) && !URL.canParse(destination)) {
+				logger.warn('redirects', 'Only links that start with http or https are supported.');
+				throw new AstroError(UnsupportedExternalRedirect);
+			}
 		}
 
 		routes.push({
diff --git a/packages/astro/test/redirects.test.js b/packages/astro/test/redirects.test.js
index 8014fb73bb45..7cbc673e6d73 100644
--- a/packages/astro/test/redirects.test.js
+++ b/packages/astro/test/redirects.test.js
@@ -36,13 +36,12 @@ describe('Astro.redirect', () => {
 			assert.equal(response.headers.get('location'), '/login');
 		});
 
-		// ref: https://github.com/withastro/astro/pull/9287#discussion_r1420739810
-		it.skip('Ignores external redirect', async () => {
+		it('Allows external redirect', async () => {
 			const app = await fixture.loadTestAdapterApp();
 			const request = new Request('http://example.com/external/redirect');
 			const response = await app.render(request);
-			assert.equal(response.status, 404);
-			assert.equal(response.headers.get('location'), null);
+			assert.equal(response.status, 301);
+			assert.equal(response.headers.get('location'), 'https://example.com/');
 		});
 
 		it('Warns when used inside a component', async () => {
@@ -131,6 +130,7 @@ describe('Astro.redirect', () => {
 						'/more/old/[dynamic]': '/more/[dynamic]',
 						'/more/old/[dynamic]/[route]': '/more/[dynamic]/[route]',
 						'/more/old/[...spread]': '/more/new/[...spread]',
+						'/external/redirect': 'https://example.com/',
 					},
 				});
 				await fixture.build();
@@ -208,6 +208,12 @@ describe('Astro.redirect', () => {
 				assert.equal(html.includes('http-equiv="refresh'), true);
 				assert.equal(html.includes('url=/more/new/welcome/world'), true);
 			});
+
+			it('supports redirecting to an external redirects', async () => {
+				const html = await fixture.readFile('/external/redirect/index.html');
+				assert.equal(html.includes('http-equiv="refresh'), true);
+				assert.equal(html.includes('url=https://example.com/'), true);
+			});
 		});
 
 		describe('dev', () => {