diff --git a/astro.config.ts b/astro.config.ts
index 8f1b5bb02..124fcaffc 100644
--- a/astro.config.ts
+++ b/astro.config.ts
@@ -208,6 +208,7 @@ export default defineConfig({
         alias: [
           { find: "@components", replacement: new URL("./src/components", import.meta.url).pathname },
           { find: "@constants", replacement: new URL("./src/constants.ts", import.meta.url).pathname },
+          { find: "@lib", replacement: new URL("./src/lib", import.meta.url).pathname },
           // Resolve scripts subpath to the package so ThemeSelect.astro / SDKSelect.astro keep working.
           {
             find: "@stainless-api/docs/components/scripts",
diff --git a/src/components/Header.astro b/src/components/Header.astro
index 07f2e1619..2e2f6ce35 100644
--- a/src/components/Header.astro
+++ b/src/components/Header.astro
@@ -17,6 +17,7 @@ import SiteTitle from "virtual:starlight/components/SiteTitle";
 import ThemeSelect from "virtual:starlight/components/ThemeSelect";
 import { HEADER_LINKS, TABS } from "virtual:stl-docs-virtual-module";
 import { Button } from "@stainless-api/ui-primitives";
+import { bannerConfig } from "@lib/banner-config";
 import MobileNavTabLinks from "./MobileNavTabLinks.astro";
 import NavTabsWithDropdown from "./NavTabsWithDropdown.astro";
 import SplashMobileMenuToggle from "./SplashMobileMenuToggle.astro";
@@ -33,6 +34,8 @@ const { hasSidebar } = Astro.locals.starlightRoute;
 const showMobileTabStrip = TABS.length > 0;
 ---
 
+{bannerConfig.enabled && <div class="sl-banner" set:html={bannerConfig.content} />}
+
 <div
   class:list={[
     "header",
diff --git a/src/content.config.ts b/src/content.config.ts
index ee3be9d89..ff790ac8b 100644
--- a/src/content.config.ts
+++ b/src/content.config.ts
@@ -140,6 +140,17 @@ const noindexSchema = z.object({
   noindex: z.boolean().optional(),
 });
 
+/**
+ * Sitewide banner field (optional, controlled by src/lib/banner-config.ts)
+ */
+const bannerSchema = z.object({
+  banner: z
+    .object({
+      content: z.string(),
+    })
+    .optional(),
+});
+
 export const collections = {
   docs: defineCollection({
     loader: docsLoader(),
@@ -150,7 +161,8 @@ export const collections = {
         .merge(pageLabelsSchema)
         .merge(productsSchema)
         .merge(learnMoreSchema)
-        .merge(noindexSchema),
+        .merge(noindexSchema)
+        .merge(bannerSchema),
     }),
   }),
 };
diff --git a/src/lib/banner-config.ts b/src/lib/banner-config.ts
new file mode 100644
index 000000000..7f6bc0931
--- /dev/null
+++ b/src/lib/banner-config.ts
@@ -0,0 +1,8 @@
+/**
+ * Sitewide banner configuration
+ * Toggle the banner on/off by changing `enabled` below
+ */
+export const bannerConfig = {
+  enabled: true,
+  content: 'Join us at <strong><a href="https://www.tigerdata.com/events/aggregate-2026">Tiger Data Aggregate 2026</a></strong> for workshops, talks, and networking.',
+};
diff --git a/src/styles/header.css b/src/styles/header.css
index 9a238070f..cd1ae82fa 100644
--- a/src/styles/header.css
+++ b/src/styles/header.css
@@ -154,3 +154,80 @@ main .sl-anchor-link svg,
   white-space: nowrap;
   border: 0;
 }
+
+/* ---- Sitewide Banner ---- */
+
+.sl-banner {
+  position: fixed !important;
+  top: 0 !important;
+  left: 0 !important;
+  right: 0 !important;
+  z-index: 200 !important;
+  width: 100vw !important;
+  max-width: none !important;
+  min-width: 100vw !important;
+  padding: 0.75rem var(--tiger-content-inset) !important;
+  background-color: var(--tiger-electric-yellow) !important;
+  color: var(--tiger-black) !important;
+  text-align: center !important;
+  line-height: 1.5 !important;
+  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1) !important;
+  border: none !important;
+  margin: 0 !important;
+  margin-inline: 0 !important;
+}
+
+.sl-banner a {
+  color: var(--tiger-black);
+  text-decoration: underline;
+}
+
+.sl-banner a:hover {
+  opacity: 0.7;
+}
+
+.sl-banner strong {
+  font-weight: 600;
+}
+
+/* Adjust page and header to account for fixed banner - only when banner exists */
+/* Desktop: banner is 48px + nav header ~56px = 104px total scroll padding */
+body:has(.sl-banner) {
+  padding-top: 48px;
+  scroll-padding-top: 104px;
+}
+
+body:has(.sl-banner) .right-sidebar-panel {
+  top: 104px !important;
+}
+
+body:has(.sl-banner) header,
+body:has(.sl-banner) .stl-header {
+  position: sticky !important;
+  top: 48px !important;
+  z-index: 100 !important;
+  background-color: light-dark(#ffffff, #1a1a1a) !important;
+}
+
+/* Mobile: banner is 70px + nav header ~64px = 134px total scroll padding */
+@media (max-width: 768px) {
+  .sl-banner {
+    padding: 0.75rem var(--tiger-space-lg);
+    font-size: 0.9rem;
+  }
+
+  body:has(.sl-banner) {
+    padding-top: 70px;
+    scroll-padding-top: 134px;
+  }
+
+  body:has(.sl-banner) header,
+  body:has(.sl-banner) .stl-header {
+    top: 70px !important;
+    background-color: light-dark(#ffffff, #1a1a1a) !important;
+  }
+
+  body:has(.sl-banner) .right-sidebar-panel {
+    top: 134px !important;
+  }
+}