diff --git a/news/changelog-1.9.md b/news/changelog-1.9.md
index 14f341aa6d9..1f55af4301e 100644
--- a/news/changelog-1.9.md
+++ b/news/changelog-1.9.md
@@ -32,6 +32,7 @@ All changes included in 1.9:
 - ([#11929](https://github.com/quarto-dev/quarto-cli/issues/11929)): Import all `brand.typography.fonts` in CSS, whether or not fonts are referenced by typography elements.
 - ([#13413](https://github.com/quarto-dev/quarto-cli/issues/13413)): Fix uncentered play button in `video` shortcodes from cross-reference divs. (author: @bruvellu)
 - ([#13508](https://github.com/quarto-dev/quarto-cli/issues/13508)): Add `aria-label` support to `video` shortcode for improved accessibility.
+- ([#13685](https://github.com/quarto-dev/quarto-cli/issues/13685)): Fix remote font URLs in brand extensions being incorrectly joined with the extension path, resulting in broken font imports.
 
 ### `typst`
 
diff --git a/src/core/sass/brand.ts b/src/core/sass/brand.ts
index 993fb5eac0a..51036ccbddc 100644
--- a/src/core/sass/brand.ts
+++ b/src/core/sass/brand.ts
@@ -150,6 +150,8 @@ const googleFontImportString = (description: BrandFontGoogle) => {
   }:${styleString}wght@${weights}&display=${display}');`;
 };
 
+const isExternalPath = (path: string) => /^\w+:/.test(path);
+
 const fileFontImportString = (brand: Brand, description: BrandFontFile) => {
   const pathPrefix = relative(brand.projectDir, brand.brandDir);
   const parts = [];
@@ -162,9 +164,12 @@ const fileFontImportString = (brand: Brand, description: BrandFontFile) => {
       weight = file.weight;
       style = file.style;
     }
+    const fontUrl = isExternalPath(path)
+      ? path
+      : join(pathPrefix, path).replace(/\\/g, "/");
     parts.push(`@font-face {
     font-family: '${description.family}';
-    src: url('${join(pathPrefix, path).replace(/\\/g, "/")}');
+    src: url('${fontUrl}');
     font-weight: ${weight || "normal"};
     font-style: ${style || "normal"};
 }\n`);
diff --git a/tests/docs/smoke-all/brand/typography/remote-font-extension/.gitignore b/tests/docs/smoke-all/brand/typography/remote-font-extension/.gitignore
new file mode 100644
index 00000000000..ad293093b07
--- /dev/null
+++ b/tests/docs/smoke-all/brand/typography/remote-font-extension/.gitignore
@@ -0,0 +1,2 @@
+/.quarto/
+**/*.quarto_ipynb
diff --git a/tests/docs/smoke-all/brand/typography/remote-font-extension/_extensions/my-brand/_extension.yml b/tests/docs/smoke-all/brand/typography/remote-font-extension/_extensions/my-brand/_extension.yml
new file mode 100644
index 00000000000..859925eab79
--- /dev/null
+++ b/tests/docs/smoke-all/brand/typography/remote-font-extension/_extensions/my-brand/_extension.yml
@@ -0,0 +1,8 @@
+title: My Brand
+author: Quarto
+version: 1.0.0
+quarto-required: ">=99.9.0"
+contributes:
+  metadata:
+    project:
+      brand: mybrand.yml
diff --git a/tests/docs/smoke-all/brand/typography/remote-font-extension/_extensions/my-brand/mybrand.yml b/tests/docs/smoke-all/brand/typography/remote-font-extension/_extensions/my-brand/mybrand.yml
new file mode 100644
index 00000000000..1f8fcf43c9d
--- /dev/null
+++ b/tests/docs/smoke-all/brand/typography/remote-font-extension/_extensions/my-brand/mybrand.yml
@@ -0,0 +1,8 @@
+typography:
+  fonts:
+    - family: Noto Sans
+      source: file
+      files:
+        - path: https://notofonts.github.io/latin-greek-cyrillic/fonts/NotoSans/unhinted/ttf/NotoSans-Regular.ttf
+  base:
+    family: Noto Sans
diff --git a/tests/docs/smoke-all/brand/typography/remote-font-extension/_quarto.yml b/tests/docs/smoke-all/brand/typography/remote-font-extension/_quarto.yml
new file mode 100644
index 00000000000..f98ff850162
--- /dev/null
+++ b/tests/docs/smoke-all/brand/typography/remote-font-extension/_quarto.yml
@@ -0,0 +1,5 @@
+project:
+  type: default
+format:
+  html:
+    theme: brand
diff --git a/tests/docs/smoke-all/brand/typography/remote-font-extension/remote-font-extension.qmd b/tests/docs/smoke-all/brand/typography/remote-font-extension/remote-font-extension.qmd
new file mode 100644
index 00000000000..25812585524
--- /dev/null
+++ b/tests/docs/smoke-all/brand/typography/remote-font-extension/remote-font-extension.qmd
@@ -0,0 +1,15 @@
+---
+title: Remote Font Extension Test
+_quarto:
+  tests:
+    html:
+      ensureCssRegexMatches:
+        - ['src:url\("https://notofonts\.github\.io/']
+        - ['_extensions/my-brand/https:']
+---
+
+# Remote Font Test
+
+This document tests that remote font URLs in brand extensions are handled correctly (issue #13685).
+
+{{< lipsum 1 >}}
diff --git a/tests/smoke/smoke-all.test.ts b/tests/smoke/smoke-all.test.ts
index b5aaafa6897..b92c9479aff 100644
--- a/tests/smoke/smoke-all.test.ts
+++ b/tests/smoke/smoke-all.test.ts
@@ -18,6 +18,7 @@ import { breakQuartoMd } from "../../src/core/lib/break-quarto-md.ts";
 import { parse } from "../../src/core/yaml.ts";
 import { cleanoutput } from "./render/render.ts";
 import {
+  ensureCssRegexMatches,
   ensureEpubFileRegexMatches,
   ensureDocxRegexMatches,
   ensureDocxXpath,
@@ -171,6 +172,7 @@ function resolveTestSpecs(
   const result = [];
   // deno-lint-ignore no-explicit-any
   const verifyMap: Record<string, any> = {
+    ensureCssRegexMatches,
     ensureEpubFileRegexMatches,
     ensureHtmlElements,
     ensureHtmlElementContents,
diff --git a/tests/verify.ts b/tests/verify.ts
index a38dbbd01d5..524ad8f5eed 100644
--- a/tests/verify.ts
+++ b/tests/verify.ts
@@ -584,6 +584,53 @@ export const ensureFileRegexMatches = (
   return(verifyFileRegexMatches(regexChecker)(file, matchesUntyped, noMatchesUntyped));
 };
 
+// Use this function to Regex match text in CSS files in the supporting files directory
+export const ensureCssRegexMatches = (
+  file: string,
+  matchesUntyped: (string | RegExp)[],
+  noMatchesUntyped?: (string | RegExp)[],
+): Verify => {
+  const asRegexp = (m: string | RegExp) => {
+    if (typeof m === "string") {
+      return new RegExp(m, "m");
+    }
+    return m;
+  };
+  const matches = matchesUntyped.map(asRegexp);
+  const noMatches = noMatchesUntyped?.map(asRegexp);
+
+  return {
+    name: `Inspecting CSS files for Regex matches`,
+    verify: async (_output: ExecuteOutput[]) => {
+      // Find support directory from file path
+      const [dir, stem] = dirAndStem(file);
+      const supportDir = join(dir, stem + "_files");
+
+      // Find all CSS files recursively and combine their content
+      let combinedContent = "";
+      for (const entry of walkSync(supportDir, { exts: [".css"] })) {
+        combinedContent += await Deno.readTextFile(entry.path) + "\n";
+      }
+
+      matches.forEach((regex) => {
+        assert(
+          regex.test(combinedContent),
+          `Required CSS match ${String(regex)} is missing.`,
+        );
+      });
+
+      if (noMatches) {
+        noMatches.forEach((regex) => {
+          assert(
+            !regex.test(combinedContent),
+            `Illegal CSS match ${String(regex)} was found.`,
+          );
+        });
+      }
+    },
+  };
+};
+
 // Use this function to Regex match text in the intermediate kept file
 // FIXME: do this properly without resorting on file having keep-*
 export const verifyKeepFileRegexMatches = (