diff --git a/crates/perry-ui-windows/src/ffi/widget_create.rs b/crates/perry-ui-windows/src/ffi/widget_create.rs
index 64462beeee..73a66f66d3 100644
--- a/crates/perry-ui-windows/src/ffi/widget_create.rs
+++ b/crates/perry-ui-windows/src/ffi/widget_create.rs
@@ -7,6 +7,15 @@ pub extern "C" fn perry_ui_text_create(text_ptr: i64) -> i64 {
     widgets::text::create(text_ptr as *const u8)
 }
 
+/// Create an AdBanner placeholder (#867). `unit_id_ptr` / `size_ptr` are
+/// string pointers per the `AdBanner(unitId, size)` dispatch row. This
+/// symbol was previously absent from the Windows staticlib, so any TS
+/// program using AdBanner failed at link time.
+#[no_mangle]
+pub extern "C" fn perry_ui_adbanner_create(unit_id_ptr: i64, size_ptr: i64) -> i64 {
+    widgets::ad_banner::create(unit_id_ptr as *const u8, size_ptr as *const u8)
+}
+
 /// Create a Button.
 #[no_mangle]
 pub extern "C" fn perry_ui_button_create(label_ptr: i64, on_press: f64) -> i64 {
diff --git a/crates/perry-ui-windows/src/widgets/ad_banner.rs b/crates/perry-ui-windows/src/widgets/ad_banner.rs
new file mode 100644
index 0000000000..a13f0dfc49
--- /dev/null
+++ b/crates/perry-ui-windows/src/widgets/ad_banner.rs
@@ -0,0 +1,109 @@
+//! `AdBanner` widget (#867) — Win32 layout placeholder.
+//!
+//! Google Mobile Ads ships no first-party Windows SDK, so — exactly like
+//! the macOS backend (`perry-ui-macos/src/widgets/adbanner.rs`) — the
+//! banner is a **layout placeholder**: an empty STATIC child sized to the
+//! requested banner slot, so a `perry/ui` layout developed or previewed
+//! on Windows reserves exactly the space the real ad occupies on
+//! iOS/Android. The `unitId` is accepted for cross-platform API parity
+//! but unused since nothing loads.
+//!
+//! Before this existed, `perry_ui_adbanner_create` was simply absent from
+//! the Windows staticlib: any TS program using `AdBanner(...)` failed at
+//! link time with an unresolved external (the symbol is a required
+//! dispatch row in `perry-dispatch/src/ui_table/part_a.rs`).
+
+#[cfg(target_os = "windows")]
+use windows::Win32::Foundation::*;
+#[cfg(target_os = "windows")]
+use windows::Win32::System::LibraryLoader::GetModuleHandleW;
+#[cfg(target_os = "windows")]
+use windows::Win32::UI::WindowsAndMessaging::*;
+
+use super::{alloc_control_id, register_widget, WidgetKind};
+
+fn str_from_header(ptr: *const u8) -> &'static str {
+    if ptr.is_null() {
+        return "";
+    }
+    unsafe {
+        let header = ptr as *const perry_runtime::string::StringHeader;
+        let len = (*header).byte_len as usize;
+        let data = ptr.add(std::mem::size_of::<perry_runtime::string::StringHeader>());
+        // Checked parse, not from_utf8_unchecked: runtime strings are WTF-8
+        // and may contain lone surrogates, which would be UB to expose as
+        // &str. An invalid size key falls back to "" → the default 320×50
+        // banner slot.
+        std::str::from_utf8(std::slice::from_raw_parts(data, len)).unwrap_or("")
+    }
+}
+
+#[cfg(target_os = "windows")]
+fn to_wide(s: &str) -> Vec<u16> {
+    s.encode_utf16().chain(std::iter::once(0)).collect()
+}
+
+/// Banner dimensions in logical pixels for each size key the d.ts exposes.
+/// Values match Google Mobile Ads' standard `AdSize` constants (and the
+/// macOS placeholder) so the reserved slot lines up with the real
+/// iOS/Android banner.
+fn banner_size(size_key: &str) -> (f64, f64) {
+    match size_key {
+        "large-banner" => (320.0, 100.0),
+        "medium-rectangle" => (300.0, 250.0),
+        "full-banner" => (468.0, 60.0),
+        "leaderboard" => (728.0, 90.0),
+        // "banner" / "adaptive" / empty / unknown → standard 320×50.
+        _ => (320.0, 50.0),
+    }
+}
+
+/// Create the banner placeholder sized per `size_ptr`. Returns the widget
+/// handle. The slot dimensions are pinned via fixed width/height so the
+/// stack layout reserves them exactly (matching the macOS NSView frame).
+pub fn create(unit_id_ptr: *const u8, size_ptr: *const u8) -> i64 {
+    let _unit_id = str_from_header(unit_id_ptr);
+    let size_key = str_from_header(size_ptr);
+    let (w, h) = banner_size(size_key);
+    let scale = crate::app::get_dpi_scale();
+    let w = (w * scale).round() as i32;
+    let h = (h * scale).round() as i32;
+    let control_id = alloc_control_id();
+
+    #[cfg(target_os = "windows")]
+    {
+        let class_name = to_wide("STATIC");
+        let window_text = to_wide("");
+        unsafe {
+            let hinstance = GetModuleHandleW(None).unwrap();
+            let hwnd = CreateWindowExW(
+                WINDOW_EX_STYLE::default(),
+                windows::core::PCWSTR(class_name.as_ptr()),
+                windows::core::PCWSTR(window_text.as_ptr()),
+                WINDOW_STYLE(WS_CHILD.0 | WS_VISIBLE.0),
+                0,
+                0,
+                w,
+                h,
+                Some(super::get_parking_hwnd()),
+                Some(HMENU(control_id as *mut _)),
+                Some(HINSTANCE::from(hinstance)),
+                None,
+            )
+            .unwrap();
+
+            let handle = register_widget(hwnd, WidgetKind::Image, control_id);
+            super::set_fixed_width(handle, w);
+            super::set_fixed_height(handle, h);
+            handle
+        }
+    }
+
+    #[cfg(not(target_os = "windows"))]
+    {
+        let handle = register_widget(0, WidgetKind::Image, control_id);
+        super::set_fixed_width(handle, w);
+        super::set_fixed_height(handle, h);
+        handle
+    }
+}
diff --git a/crates/perry-ui-windows/src/widgets/mod.rs b/crates/perry-ui-windows/src/widgets/mod.rs
index 1311f552bb..8b09ba1950 100644
--- a/crates/perry-ui-windows/src/widgets/mod.rs
+++ b/crates/perry-ui-windows/src/widgets/mod.rs
@@ -1,6 +1,7 @@
 //! Widget registry — Vec<WidgetEntry> with 1-based handles.
 //! Each widget has an HWND (on Windows), a kind, children list, and layout info.
 
+pub mod ad_banner;
 pub mod attributed_text;
 pub mod bloomview;
 pub mod bottom_nav;