diff --git a/Libraries/LibWebView/Application.cpp b/Libraries/LibWebView/Application.cpp
index 57c2f54c28..9a55df0211 100644
--- a/Libraries/LibWebView/Application.cpp
+++ b/Libraries/LibWebView/Application.cpp
@@ -1203,6 +1203,7 @@ void Application::clear_browsing_data(ClearBrowsingDataOptions const& options)
     if (options.delete_site_data == ClearBrowsingDataOptions::Delete::Yes) {
         m_cookie_jar->expire_cookies_accessed_since(options.since);
         m_storage_jar->remove_items_accessed_since(options.since);
+        m_hsts_store->remove_policies_observed_since(options.since);
     }
 
     if (did_change_history)
diff --git a/Libraries/LibWebView/HSTSStore.cpp b/Libraries/LibWebView/HSTSStore.cpp
index d074fcc28e..6991f12ec8 100644
--- a/Libraries/LibWebView/HSTSStore.cpp
+++ b/Libraries/LibWebView/HSTSStore.cpp
@@ -134,6 +134,11 @@ bool HSTSStore::is_known_hsts_host(StringView domain)
     return false;
 }
 
+void HSTSStore::remove_policies_observed_since(UnixDateTime since)
+{
+    m_transient_storage.remove_policies_observed_since(since);
+}
+
 void HSTSStore::TransientStorage::set_policies(Policies policies)
 {
     m_policies = move(policies);
@@ -168,6 +173,18 @@ void HSTSStore::TransientStorage::update_last_observed_time(StringView domain)
     m_dirty_policies.set(it->key, it->value);
 }
 
+void HSTSStore::TransientStorage::remove_policies_observed_since(UnixDateTime since)
+{
+    for (auto& [domain, policy] : m_policies) {
+        if (policy.last_observed_time >= since) {
+            policy.expiry = UnixDateTime::earliest();
+            m_dirty_policies.set(domain, policy);
+        }
+    }
+
+    purge_expired_policies();
+}
+
 UnixDateTime HSTSStore::TransientStorage::purge_expired_policies()
 {
     // A Known HSTS Host is "expired" if its cache entry has an expiry date
diff --git a/Libraries/LibWebView/HSTSStore.h b/Libraries/LibWebView/HSTSStore.h
index ed3e316b72..ff2f979303 100644
--- a/Libraries/LibWebView/HSTSStore.h
+++ b/Libraries/LibWebView/HSTSStore.h
@@ -29,6 +29,8 @@ public:
     // https://www.rfc-editor.org/rfc/rfc6797#section-8.2
     bool is_known_hsts_host(StringView domain);
 
+    void remove_policies_observed_since(UnixDateTime since);
+
 private:
     struct StoredPolicy {
         UnixDateTime expiry;
@@ -52,6 +54,7 @@ private:
         void update_last_observed_time(StringView domain);
 
         UnixDateTime purge_expired_policies();
+        void remove_policies_observed_since(UnixDateTime since);
 
         auto take_dirty_policies() { return move(m_dirty_policies); }