diff --git a/packages/common/src/utils.ts b/packages/common/src/utils.ts
index 9058daf0a..943c287f6 100644
--- a/packages/common/src/utils.ts
+++ b/packages/common/src/utils.ts
@@ -172,7 +172,12 @@ export function updateSiteManifestStaticLinksInplace(
   if (data.options.logo) data.options.logo = updateUrl(data.options.logo);
   if (data.options.logo_dark) data.options.logo_dark = updateUrl(data.options.logo_dark);
   if (data.options.favicon) data.options.favicon = updateUrl(data.options.favicon);
-  if (data.options.style) data.options.style = updateUrl(data.options.style);
+  if (data.options.style) {
+    // `style` may be a single link or, for a `multiple` file option, a list.
+    data.options.style = Array.isArray(data.options.style)
+      ? data.options.style.map(updateUrl)
+      : updateUrl(data.options.style);
+  }
   if (data.parts) {
     Object.values(data.parts).forEach(({ mdast }) => {
       updateMdastStaticLinksInplace(mdast, updateUrl);
diff --git a/themes/article/app/utils/loaders.server.ts b/themes/article/app/utils/loaders.server.ts
index 432d031d8..f5beba2bc 100644
--- a/themes/article/app/utils/loaders.server.ts
+++ b/themes/article/app/utils/loaders.server.ts
@@ -149,12 +149,25 @@ export async function getFavicon(): Promise<{
 export async function getCustomStyleSheet(): Promise<string | undefined> {
   // We are always fetching this at run time, so we don't want the rewritten links
   const config = await getConfig({ rewriteStaticFolder: false });
-  const url = config.options?.style;
-  if (!url) {
+  // `style` may be a single URL or, since the option is declared `multiple`, a
+  // list of them. Normalize to an array, fetch each, and concatenate in order
+  // so later stylesheets override earlier ones.
+  const style = config.options?.style;
+  const urls = (Array.isArray(style) ? style : [style]).filter(Boolean);
+  if (urls.length === 0) {
     return;
   }
-  const response = await fetch(url).catch(() => null);
-  if (!response || response.status === 404) return;
-  const css = await response.text();
-  return css;
+  const sheets = await Promise.all(
+    urls.map(async (url) => {
+      const response = await fetch(url).catch(() => null);
+      if (!response || response.status === 404) return undefined;
+      try {
+        return response.text();
+      } catch {
+        return undefined;
+      }
+    }),
+  );
+  const css = sheets.filter(Boolean).join('\n\n');
+  return css || undefined;
 }
diff --git a/themes/article/template.yml b/themes/article/template.yml
index 19b294c62..c33d617be 100644
--- a/themes/article/template.yml
+++ b/themes/article/template.yml
@@ -71,7 +71,8 @@ options:
       Supports wildcard subdomains with *. Example: "jupyter.org" or "*.jupyter.org"
   - type: file
     id: style
-    description: Local path to a CSS file
+    multiple: true
+    description: URL to fetch, or a list of them (applied in order)
 build:
   install: npm ci --ignore-scripts
   start: npm run start
diff --git a/themes/book/app/utils/loaders.server.ts b/themes/book/app/utils/loaders.server.ts
index 81a657b37..bbebb7ab2 100644
--- a/themes/book/app/utils/loaders.server.ts
+++ b/themes/book/app/utils/loaders.server.ts
@@ -150,12 +150,25 @@ export async function getFavicon(): Promise<{
 export async function getCustomStyleSheet(): Promise<string | undefined> {
   // We are always fetching this at run time, so we don't want the rewritten links
   const config = await getConfig({ rewriteStaticFolder: false });
-  const url = config.options?.style;
-  if (!url) {
+  // `style` may be a single URL or, since the option is declared `multiple`, a
+  // list of them. Normalize to an array, fetch each, and concatenate in order
+  // so later stylesheets override earlier ones.
+  const style = config.options?.style;
+  const urls = (Array.isArray(style) ? style : [style]).filter(Boolean);
+  if (urls.length === 0) {
     return;
   }
-  const response = await fetch(url).catch(() => null);
-  if (!response || response.status === 404) return;
-  const css = await response.text();
-  return css;
+  const sheets = await Promise.all(
+    urls.map(async (url) => {
+      const response = await fetch(url).catch(() => null);
+      if (!response || response.status === 404) return undefined;
+      try {
+        return response.text();
+      } catch {
+        return undefined;
+      }
+    }),
+  );
+  const css = sheets.filter(Boolean).join('\n\n');
+  return css || undefined;
 }
diff --git a/themes/book/template.yml b/themes/book/template.yml
index a10976462..8bf2c9178 100644
--- a/themes/book/template.yml
+++ b/themes/book/template.yml
@@ -77,7 +77,8 @@ options:
       Supports wildcard subdomains with *. Example: "jupyter.org" or "*.jupyter.org"
   - type: file
     id: style
-    description: Local path to a CSS file
+    multiple: true
+    description: URL to fetch, or a list of them (applied in order)
 parts:
   - id: footer
     description: The site wide footer