diff --git a/Libraries/LibWeb/HTML/Navigable.cpp b/Libraries/LibWeb/HTML/Navigable.cpp
index 6072da8ee73..a5f4c709966 100644
--- a/Libraries/LibWeb/HTML/Navigable.cpp
+++ b/Libraries/LibWeb/HTML/Navigable.cpp
@@ -1349,6 +1349,12 @@ WebIDL::ExceptionOr<void> Navigable::navigate(NavigateParams params)
     auto& active_document = *this->active_document();
     auto& realm = active_document.realm();
 
+    // AD-HOC: If we are not able to continue in this process, request a new process from the UI.
+    if (!active_document.page().client().is_url_suitable_for_same_process_navigation(active_document.url(), params.url)) {
+        active_document.page().client().request_new_process_for_navigation(params.url);
+        return {};
+    }
+
     // 2. Let sourceSnapshotParams be the result of snapshotting source snapshot params given sourceDocument.
     auto source_snapshot_params = source_document->snapshot_source_snapshot_params();
 
diff --git a/Libraries/LibWeb/Page/Page.h b/Libraries/LibWeb/Page/Page.h
index 47b77e287fb..9704c71b046 100644
--- a/Libraries/LibWeb/Page/Page.h
+++ b/Libraries/LibWeb/Page/Page.h
@@ -321,6 +321,8 @@ public:
     virtual Page& page() = 0;
     virtual Page const& page() const = 0;
     virtual bool is_connection_open() const = 0;
+    virtual bool is_url_suitable_for_same_process_navigation([[maybe_unused]] URL::URL const& current_url, [[maybe_unused]] URL::URL const& target_url) const { return true; }
+    virtual void request_new_process_for_navigation(URL::URL const&) { }
     virtual Gfx::Palette palette() const = 0;
     virtual DevicePixelRect screen_rect() const = 0;
     virtual double device_pixels_per_css_pixel() const = 0;
diff --git a/Libraries/LibWebView/CMakeLists.txt b/Libraries/LibWebView/CMakeLists.txt
index bbab6874b47..acd6e5c8ac3 100644
--- a/Libraries/LibWebView/CMakeLists.txt
+++ b/Libraries/LibWebView/CMakeLists.txt
@@ -16,6 +16,7 @@ set(SOURCES
     ProcessHandle.cpp
     ProcessManager.cpp
     SearchEngine.cpp
+    SiteIsolation.cpp
     SourceHighlighter.cpp
     URL.cpp
     UserAgent.cpp
diff --git a/Libraries/LibWebView/SiteIsolation.cpp b/Libraries/LibWebView/SiteIsolation.cpp
new file mode 100644
index 00000000000..93584ca121b
--- /dev/null
+++ b/Libraries/LibWebView/SiteIsolation.cpp
@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2025, Tim Flynn <trflynn89@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibURL/URL.h>
+#include <LibWeb/Fetch/Infrastructure/URL.h>
+#include <LibWeb/HTML/BrowsingContext.h>
+#include <LibWebView/SiteIsolation.h>
+
+namespace WebView {
+
+bool is_url_suitable_for_same_process_navigation(URL::URL const& current_url, URL::URL const& target_url)
+{
+    // Allow navigating from about:blank to any site.
+    if (Web::HTML::url_matches_about_blank(current_url))
+        return true;
+
+    // Allow cross-scheme non-HTTP(S) navigation. Disallow cross-scheme HTTP(s) navigation.
+    auto current_url_is_http = Web::Fetch::Infrastructure::is_http_or_https_scheme(current_url.scheme());
+    auto target_url_is_http = Web::Fetch::Infrastructure::is_http_or_https_scheme(target_url.scheme());
+
+    if (!current_url_is_http || !target_url_is_http)
+        return !current_url_is_http && !target_url_is_http;
+
+    // Disallow cross-site HTTP(S) navigation.
+    return current_url.origin().is_same_site(target_url.origin());
+}
+
+}
diff --git a/Libraries/LibWebView/SiteIsolation.h b/Libraries/LibWebView/SiteIsolation.h
new file mode 100644
index 00000000000..c31c8c1bf78
--- /dev/null
+++ b/Libraries/LibWebView/SiteIsolation.h
@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2025, Tim Flynn <trflynn89@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibURL/Forward.h>
+
+namespace WebView {
+
+[[nodiscard]] bool is_url_suitable_for_same_process_navigation(URL::URL const& current_url, URL::URL const& target_url);
+
+}
diff --git a/Libraries/LibWebView/ViewImplementation.cpp b/Libraries/LibWebView/ViewImplementation.cpp
index 271e334d5f3..3358847f5da 100644
--- a/Libraries/LibWebView/ViewImplementation.cpp
+++ b/Libraries/LibWebView/ViewImplementation.cpp
@@ -14,6 +14,7 @@
 #include <LibWeb/Infra/Strings.h>
 #include <LibWebView/Application.h>
 #include <LibWebView/HelperProcess.h>
+#include <LibWebView/SiteIsolation.h>
 #include <LibWebView/UserAgent.h>
 #include <LibWebView/ViewImplementation.h>
 
@@ -89,6 +90,21 @@ u64 ViewImplementation::page_id() const
     return m_client_state.page_index;
 }
 
+void ViewImplementation::create_new_process_for_cross_site_navigation(URL::URL const& url)
+{
+    if (m_client_state.client)
+        client().async_close_server();
+
+    initialize_client();
+    VERIFY(m_client_state.client);
+
+    // Don't keep a stale backup bitmap around.
+    m_backup_bitmap = nullptr;
+    handle_resize();
+
+    load(url);
+}
+
 void ViewImplementation::server_did_paint(Badge<WebContentClient>, i32 bitmap_id, Gfx::IntSize size)
 {
     if (m_client_state.back_bitmap.id == bitmap_id) {
diff --git a/Libraries/LibWebView/ViewImplementation.h b/Libraries/LibWebView/ViewImplementation.h
index 70dcb1eee26..c1f8ed73592 100644
--- a/Libraries/LibWebView/ViewImplementation.h
+++ b/Libraries/LibWebView/ViewImplementation.h
@@ -58,6 +58,8 @@ public:
 
     String const& handle() const { return m_client_state.client_handle; }
 
+    void create_new_process_for_cross_site_navigation(URL::URL const&);
+
     void server_did_paint(Badge<WebContentClient>, i32 bitmap_id, Gfx::IntSize size);
 
     void set_window_position(Gfx::IntPoint);
diff --git a/Libraries/LibWebView/WebContentClient.cpp b/Libraries/LibWebView/WebContentClient.cpp
index f4cbf963e25..29d664096d9 100644
--- a/Libraries/LibWebView/WebContentClient.cpp
+++ b/Libraries/LibWebView/WebContentClient.cpp
@@ -62,6 +62,12 @@ void WebContentClient::did_paint(u64 page_id, Gfx::IntRect rect, i32 bitmap_id)
         view->server_did_paint({}, bitmap_id, rect.size());
 }
 
+void WebContentClient::did_request_new_process_for_navigation(u64 page_id, URL::URL url)
+{
+    if (auto view = view_for_page_id(page_id); view.has_value())
+        view->create_new_process_for_cross_site_navigation(url);
+}
+
 void WebContentClient::did_start_loading(u64 page_id, URL::URL url, bool is_redirect)
 {
     if (auto process = WebView::Application::the().find_process(m_process_handle.pid); process.has_value())
diff --git a/Libraries/LibWebView/WebContentClient.h b/Libraries/LibWebView/WebContentClient.h
index 06eec41a253..28dd0d71376 100644
--- a/Libraries/LibWebView/WebContentClient.h
+++ b/Libraries/LibWebView/WebContentClient.h
@@ -52,6 +52,7 @@ private:
     virtual void die() override;
 
     virtual void did_paint(u64 page_id, Gfx::IntRect, i32) override;
+    virtual void did_request_new_process_for_navigation(u64 page_id, URL::URL url) override;
     virtual void did_finish_loading(u64 page_id, URL::URL) override;
     virtual void did_request_refresh(u64 page_id) override;
     virtual void did_request_cursor_change(u64 page_id, Gfx::Cursor) override;
diff --git a/Services/WebContent/PageClient.cpp b/Services/WebContent/PageClient.cpp
index 1049fef6aa8..2e917bae179 100644
--- a/Services/WebContent/PageClient.cpp
+++ b/Services/WebContent/PageClient.cpp
@@ -29,6 +29,7 @@
 #include <LibWeb/Painting/PaintableBox.h>
 #include <LibWeb/Painting/ViewportPaintable.h>
 #include <LibWebView/Attribute.h>
+#include <LibWebView/SiteIsolation.h>
 #include <WebContent/ConnectionFromClient.h>
 #include <WebContent/DevToolsConsoleClient.h>
 #include <WebContent/InspectorConsoleClient.h>
@@ -134,6 +135,16 @@ bool PageClient::is_connection_open() const
     return client().is_open();
 }
 
+bool PageClient::is_url_suitable_for_same_process_navigation(URL::URL const& current_url, URL::URL const& target_url) const
+{
+    return WebView::is_url_suitable_for_same_process_navigation(current_url, target_url);
+}
+
+void PageClient::request_new_process_for_navigation(URL::URL const& url)
+{
+    client().async_did_request_new_process_for_navigation(m_id, url);
+}
+
 Gfx::Palette PageClient::palette() const
 {
     return Gfx::Palette(*m_palette_impl);
diff --git a/Services/WebContent/PageClient.h b/Services/WebContent/PageClient.h
index a7a5029a4a7..f3ea3df8a35 100644
--- a/Services/WebContent/PageClient.h
+++ b/Services/WebContent/PageClient.h
@@ -111,6 +111,8 @@ private:
 
     // ^PageClient
     virtual bool is_connection_open() const override;
+    virtual bool is_url_suitable_for_same_process_navigation(URL::URL const& current_url, URL::URL const& target_url) const override;
+    virtual void request_new_process_for_navigation(URL::URL const&) override;
     virtual Gfx::Palette palette() const override;
     virtual Web::DevicePixelRect screen_rect() const override { return m_screen_rect; }
     virtual Web::CSS::PreferredColorScheme preferred_color_scheme() const override { return m_preferred_color_scheme; }
diff --git a/Services/WebContent/WebContentClient.ipc b/Services/WebContent/WebContentClient.ipc
index 766a8dbb1e6..42e71257772 100644
--- a/Services/WebContent/WebContentClient.ipc
+++ b/Services/WebContent/WebContentClient.ipc
@@ -23,6 +23,7 @@
 
 endpoint WebContentClient
 {
+    did_request_new_process_for_navigation(u64 page_id, URL::URL url) =|
     did_start_loading(u64 page_id, URL::URL url, bool is_redirect) =|
     did_finish_loading(u64 page_id, URL::URL url) =|
     did_request_refresh(u64 page_id) =|