diff --git a/docs/astro.config.mjs b/docs/astro.config.mjs
index 88b8b0bb..e4116184 100644
--- a/docs/astro.config.mjs
+++ b/docs/astro.config.mjs
@@ -1,6 +1,7 @@
 // @ts-check
 import { defineConfig } from 'astro/config';
 import starlight from '@astrojs/starlight';
+import { siteLinks } from './src/site-links.ts';
 
 // https://astro.build/config
 export default defineConfig({
@@ -59,8 +60,10 @@ export default defineConfig({
 						{ label: 'FAQ', slug: 'faq' },
 						{ label: 'Known Issues', slug: 'knownissues' },
 						{ label: 'Contributing', slug: 'contributing' },
+						{ label: siteLinks.forums.label, link: siteLinks.forums.href, attrs: { target: '_blank', rel: 'noreferrer' } },
 					],
 				},
+				{ label: siteLinks.store.label, link: siteLinks.store.href, attrs: { target: '_blank', rel: 'noreferrer' } },
 			],
 		}),
 	],
diff --git a/docs/src/components/Header.astro b/docs/src/components/Header.astro
index 9a5007b8..faf02ea0 100644
--- a/docs/src/components/Header.astro
+++ b/docs/src/components/Header.astro
@@ -6,10 +6,15 @@ import Search from 'virtual:starlight/components/Search';
 import SiteTitle from 'virtual:starlight/components/SiteTitle';
 import SocialIcons from 'virtual:starlight/components/SocialIcons';
 import ThemeSelect from 'virtual:starlight/components/ThemeSelect';
+import { Icon } from '@astrojs/starlight/components';
+import { siteLinks } from '../site-links';
 
 // Render the `Search` component if Pagefind is enabled or the default search component has been overridden.
 const shouldRenderSearch =
 	config.pagefind || config.components.Search !== '@astrojs/starlight/components/Search.astro';
+
+// Pages with a sidebar already have Starlight's own mobile menu toggle; only splash pages need this one.
+const { hasSidebar } = Astro.locals.starlightRoute;
 ---
 
 <div class="header">
@@ -17,9 +22,36 @@ const shouldRenderSearch =
 	<div class="title-wrapper sl-flex">
 		<SiteTitle />
 	</div>
-	{/* Search box. */}
-	<div class="sl-flex print:hidden">
-		{shouldRenderSearch && <Search />}
+	<div class="mobile-actions sl-flex">
+		{/* Search box. */}
+		<div class="sl-flex print:hidden">
+			{shouldRenderSearch && <Search />}
+		</div>
+		{
+			!hasSidebar && (
+				<div class="site-nav-toggle sl-flex md:sl-hidden print:hidden">
+					<button type="button" aria-expanded="false" aria-controls="site-nav-panel" aria-label="Site navigation">
+						<Icon name="bars" class="open-menu" />
+						<Icon name="close" class="close-menu" />
+					</button>
+					<div id="site-nav-panel" class="site-nav-panel">
+						<div class="site-nav-panel-group">
+							<p class="site-nav-panel-heading">Documentation</p>
+							<a href="/guides/">User Guides</a>
+							<a href="/contributing/">Contribution Guides</a>
+							<a href="/code-reference/architecture/">Code Reference</a>
+						</div>
+						<div class="site-nav-panel-group">
+							<p class="site-nav-panel-heading">Help</p>
+							<a href="/faq/">FAQ</a>
+							<a href="/knownissues/">Known Issues</a>
+							<a href={siteLinks.forums.href} target="_blank" rel="noreferrer">{siteLinks.forums.label}</a>
+						</div>
+						<a class="site-nav-panel-link" href={siteLinks.store.href} target="_blank" rel="noreferrer">{siteLinks.store.label}</a>
+					</div>
+				</div>
+			)
+		}
 	</div>
 	{/* Right-side group: nav links, social icons, theme/language pickers. */}
 	<div class="sl-hidden md:sl-flex print:hidden right-group">
@@ -43,10 +75,10 @@ const shouldRenderSearch =
 				<div class="site-nav-menu">
 					<a href="/faq/">FAQ</a>
 					<a href="/knownissues/">Known Issues</a>
-					<a href="https://forum.christitus.com/" target="_blank" rel="noreferrer">Forums</a>
+					<a href={siteLinks.forums.href} target="_blank" rel="noreferrer">{siteLinks.forums.label}</a>
 				</div>
 			</div>
-			<a class="site-nav-link" href="https://christitus.com/downloads/" target="_blank" rel="noreferrer">Store</a>
+			<a class="site-nav-link" href={siteLinks.store.href} target="_blank" rel="noreferrer">{siteLinks.store.label}</a>
 		</nav>
 		<div class="sl-flex social-icons">
 			<SocialIcons />
@@ -56,6 +88,25 @@ const shouldRenderSearch =
 	</div>
 </div>
 
+<script>
+	const toggle = document.querySelector<HTMLElement>('.site-nav-toggle');
+	const btn = toggle?.querySelector('button');
+
+	if (toggle && btn) {
+		const setExpanded = (expanded: boolean) => btn.setAttribute('aria-expanded', String(expanded));
+
+		btn.addEventListener('click', () => setExpanded(btn.getAttribute('aria-expanded') !== 'true'));
+		toggle.addEventListener('keyup', (e) => {
+			if (e.code === 'Escape') {
+				setExpanded(false);
+				btn.focus();
+			}
+		});
+		// Collapse the panel if the viewport grows past the mobile breakpoint.
+		matchMedia('(min-width: 50em)').addEventListener('change', () => setExpanded(false));
+	}
+</script>
+
 <style>
 	@layer starlight.core {
 		/* Header shell: title, search, right-side nav group. */
@@ -75,6 +126,11 @@ const shouldRenderSearch =
 			min-width: 0;
 		}
 
+		.mobile-actions {
+			align-items: center;
+			gap: 0.75rem;
+		}
+
 		/* Right-side group: nav + social icons, divided by a hairline. */
 		.right-group,
 		.social-icons {
@@ -194,4 +250,82 @@ const shouldRenderSearch =
 		color: var(--sl-color-white);
 		background: var(--sl-color-gray-6);
 	}
+
+	/* Mobile equivalent of the site-nav, shown via a toggle button since the desktop nav is hidden below `md`. */
+	.site-nav-toggle button {
+		display: flex;
+		align-items: center;
+		justify-content: center;
+		width: 2.25rem;
+		height: 2.25rem;
+		border: 0;
+		border-radius: var(--wu-radius-sm, 0.5rem);
+		padding: 0;
+		background: none;
+		color: var(--sl-color-gray-2);
+		cursor: pointer;
+	}
+	.site-nav-toggle button:hover {
+		color: var(--sl-color-white);
+	}
+	.site-nav-toggle button svg {
+		width: 1.25rem;
+		height: 1.25rem;
+	}
+	.site-nav-toggle button[aria-expanded='true'] .open-menu,
+	.site-nav-toggle button:not([aria-expanded='true']) .close-menu {
+		display: none;
+	}
+
+	.site-nav-panel {
+		display: none;
+		position: fixed;
+		inset-inline: 0;
+		top: var(--sl-nav-height);
+		z-index: var(--sl-z-index-menu);
+		flex-direction: column;
+		gap: 0.25rem;
+		max-height: calc(100vh - var(--sl-nav-height));
+		overflow-y: auto;
+		padding: 1rem var(--sl-nav-pad-x) 1.5rem;
+		background: var(--sl-color-bg-nav);
+		border-bottom: 1px solid var(--sl-color-hairline-shade);
+	}
+	.site-nav-toggle button[aria-expanded='true'] ~ .site-nav-panel {
+		display: flex;
+	}
+	.site-nav-panel-link {
+		padding: 0.5rem 0.25rem;
+		font-size: var(--sl-text-sm);
+		font-weight: 500;
+		color: var(--sl-color-gray-2);
+		text-decoration: none;
+	}
+	.site-nav-panel-link:hover {
+		color: var(--sl-color-white);
+	}
+	.site-nav-panel-group {
+		display: flex;
+		flex-direction: column;
+		border-top: 1px solid var(--sl-color-hairline-light);
+		padding-top: 0.5rem;
+	}
+	.site-nav-panel-heading {
+		margin: 0 0 0.25rem;
+		padding: 0 0.25rem;
+		font-size: var(--sl-text-xs);
+		font-weight: 600;
+		text-transform: uppercase;
+		letter-spacing: 0.02em;
+		color: var(--sl-color-gray-3);
+	}
+	.site-nav-panel-group a {
+		padding: 0.5rem 0.25rem;
+		font-size: var(--sl-text-sm);
+		color: var(--sl-color-gray-2);
+		text-decoration: none;
+	}
+	.site-nav-panel-group a:hover {
+		color: var(--sl-color-white);
+	}
 </style>
diff --git a/docs/src/site-links.ts b/docs/src/site-links.ts
new file mode 100644
index 00000000..dc2f31aa
--- /dev/null
+++ b/docs/src/site-links.ts
@@ -0,0 +1,5 @@
+// Shared external links, so astro.config.mjs and Header.astro can't drift out of sync.
+export const siteLinks = {
+	store: { label: 'Store', href: 'https://christitus.com/downloads/' },
+	forums: { label: 'Forums', href: 'https://forum.christitus.com/' },
+} as const;