diff --git a/404.html b/404.html
new file mode 100644
index 0000000..4517abc
--- /dev/null
+++ b/404.html
@@ -0,0 +1,26 @@
+---
+layout: default
+---
+<div class="container-lg px-3">
+  <header class="py-6">
+    <div class="pb-0 pt-md-4 py-lg-6">
+      <div class="d-md-flex flex-md-items-center flex-md-row-reverse flex-md-justify-center gutter-md-spacious">
+        <div class="col-md-8 text-center text-md-left">
+          <h1 class="alt-h2 text-uppercase lh-condensed text-brand-blue">
+            <code style="font-size: 1.05em">404</code>: Page not found
+          </h1>
+          <h2 class="alt-h2 lh-condensed">
+            Something’s missing.
+          </h2>
+          <p class="alt-lead text-gray-light mt-2 lh-condensed" style="opacity: 0.6">
+            The page at this URL doesn’t exist.<br>
+            Are you looking for <a href="/">the homepage</a> or <a href="/docs">the docs?</a>
+          </p>
+        </div>
+        <div class="col-3 mx-auto mx-md-0 offset-md-1 text-center text-md-right">
+          <img src="/assets/logo.png" class="width-fit" alt="Probot logo">
+        </div>
+      </div>
+    </div>
+  </header>
+</div>