diff --git a/Libraries/LibWeb/HTML/Storage.cpp b/Libraries/LibWeb/HTML/Storage.cpp
index 33f0f5ac75d..d8c1d60ff8b 100644
--- a/Libraries/LibWeb/HTML/Storage.cpp
+++ b/Libraries/LibWeb/HTML/Storage.cpp
@@ -1,6 +1,7 @@
 /*
  * Copyright (c) 2022, Andreas Kling <andreas@ladybird.org>
  * Copyright (c) 2023, Luke Wilde <lukew@serenityos.org>
+ * Copyright (c) 2024, Shannon Booth <shannon@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -14,13 +15,14 @@ namespace Web::HTML {
 
 GC_DEFINE_ALLOCATOR(Storage);
 
-GC::Ref<Storage> Storage::create(JS::Realm& realm)
+GC::Ref<Storage> Storage::create(JS::Realm& realm, u64 quota_bytes)
 {
-    return realm.create<Storage>(realm);
+    return realm.create<Storage>(realm, quota_bytes);
 }
 
-Storage::Storage(JS::Realm& realm)
+Storage::Storage(JS::Realm& realm, u64 quota_bytes)
     : Bindings::PlatformObject(realm)
+    , m_quota_bytes(quota_bytes)
 {
     m_legacy_platform_object_flags = LegacyPlatformObjectFlags {
         .supports_indexed_properties = true,
@@ -78,6 +80,8 @@ Optional<String> Storage::get_item(StringView key) const
 // https://html.spec.whatwg.org/multipage/webstorage.html#dom-storage-setitem
 WebIDL::ExceptionOr<void> Storage::set_item(String const& key, String const& value)
 {
+    auto& realm = this->realm();
+
     // 1. Let oldValue be null.
     String old_value;
 
@@ -85,6 +89,7 @@ WebIDL::ExceptionOr<void> Storage::set_item(String const& key, String const& val
     bool reorder = true;
 
     // 3. If this's map[key] exists:
+    auto new_size = m_stored_bytes;
     if (auto it = m_map.find(key); it != m_map.end()) {
         // 1. Set oldValue to this's map[key].
         old_value = it->value;
@@ -95,12 +100,18 @@ WebIDL::ExceptionOr<void> Storage::set_item(String const& key, String const& val
 
         // 3. Set reorder to false.
         reorder = false;
+    } else {
+        new_size += key.bytes().size();
     }
 
-    // FIXME: 4. If value cannot be stored, then throw a "QuotaExceededError" DOMException exception.
+    // 4. If value cannot be stored, then throw a "QuotaExceededError" DOMException exception.
+    new_size += value.bytes().size() - old_value.bytes().size();
+    if (new_size > m_quota_bytes)
+        return WebIDL::QuotaExceededError::create(realm, MUST(String::formatted("Unable to store more than {} bytes in storage"sv, m_quota_bytes)));
 
     // 5. Set this's map[key] to value.
     m_map.set(key, value);
+    m_stored_bytes = new_size;
 
     // 6. If reorder is true, then reorder this.
     if (reorder)
@@ -126,6 +137,7 @@ void Storage::remove_item(StringView key)
 
     // 3. Remove this's map[key].
     m_map.remove(it);
+    m_stored_bytes = m_stored_bytes - key.bytes().size() - old_value.bytes().size();
 
     // 4. Reorder this.
     reorder();
diff --git a/Libraries/LibWeb/HTML/Storage.h b/Libraries/LibWeb/HTML/Storage.h
index 33c115d52fb..4dd9a9e18e8 100644
--- a/Libraries/LibWeb/HTML/Storage.h
+++ b/Libraries/LibWeb/HTML/Storage.h
@@ -18,7 +18,7 @@ class Storage : public Bindings::PlatformObject {
     GC_DECLARE_ALLOCATOR(Storage);
 
 public:
-    [[nodiscard]] static GC::Ref<Storage> create(JS::Realm&);
+    [[nodiscard]] static GC::Ref<Storage> create(JS::Realm&, u64 quota_bytes);
     ~Storage();
 
     size_t length() const;
@@ -33,7 +33,7 @@ public:
     void dump() const;
 
 private:
-    explicit Storage(JS::Realm&);
+    explicit Storage(JS::Realm&, u64 quota_limit);
 
     virtual void initialize(JS::Realm&) override;
 
@@ -49,6 +49,8 @@ private:
     void broadcast(StringView key, StringView old_value, StringView new_value);
 
     OrderedHashMap<String, String> m_map;
+    u64 m_quota_bytes { 0 };
+    u64 m_stored_bytes { 0 };
 };
 
 }
diff --git a/Libraries/LibWeb/HTML/Window.cpp b/Libraries/LibWeb/HTML/Window.cpp
index a5e29eecb02..47628470802 100644
--- a/Libraries/LibWeb/HTML/Window.cpp
+++ b/Libraries/LibWeb/HTML/Window.cpp
@@ -447,10 +447,13 @@ void Window::fire_a_page_transition_event(FlyString const& event_name, bool pers
 // https://html.spec.whatwg.org/multipage/webstorage.html#dom-localstorage
 WebIDL::ExceptionOr<GC::Ref<Storage>> Window::local_storage()
 {
+    // See table in: https://storage.spec.whatwg.org/#registered-storage-endpoints
+    constexpr u64 quota_bytes = 5 * MiB;
+
     // FIXME: Implement according to spec.
     static HashMap<URL::Origin, GC::Root<Storage>> local_storage_per_origin;
     auto storage = local_storage_per_origin.ensure(associated_document().origin(), [this]() -> GC::Root<Storage> {
-        return Storage::create(realm());
+        return Storage::create(realm(), quota_bytes);
     });
     return GC::Ref { *storage };
 }
@@ -458,10 +461,13 @@ WebIDL::ExceptionOr<GC::Ref<Storage>> Window::local_storage()
 // https://html.spec.whatwg.org/multipage/webstorage.html#dom-sessionstorage
 WebIDL::ExceptionOr<GC::Ref<Storage>> Window::session_storage()
 {
+    // See table in: https://storage.spec.whatwg.org/#registered-storage-endpoints
+    constexpr u64 quota_bytes = 5 * MiB;
+
     // FIXME: Implement according to spec.
     static HashMap<URL::Origin, GC::Root<Storage>> session_storage_per_origin;
     auto storage = session_storage_per_origin.ensure(associated_document().origin(), [this]() -> GC::Root<Storage> {
-        return Storage::create(realm());
+        return Storage::create(realm(), quota_bytes);
     });
     return GC::Ref { *storage };
 }
diff --git a/Tests/LibWeb/Text/expected/wpt-import/webstorage/storage_local_setitem_quotaexceedederr.window.txt b/Tests/LibWeb/Text/expected/wpt-import/webstorage/storage_local_setitem_quotaexceedederr.window.txt
new file mode 100644
index 00000000000..4327c6a04e8
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/webstorage/storage_local_setitem_quotaexceedederr.window.txt
@@ -0,0 +1 @@
+QuotaExceededError: Unable to store more than 5242880 bytes in storage
diff --git a/Tests/LibWeb/Text/expected/wpt-import/webstorage/storage_session_setitem_quotaexceedederr.window.txt b/Tests/LibWeb/Text/expected/wpt-import/webstorage/storage_session_setitem_quotaexceedederr.window.txt
new file mode 100644
index 00000000000..4327c6a04e8
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/webstorage/storage_session_setitem_quotaexceedederr.window.txt
@@ -0,0 +1 @@
+QuotaExceededError: Unable to store more than 5242880 bytes in storage
diff --git a/Tests/LibWeb/Text/input/wpt-import/webstorage/storage_local_setitem_quotaexceedederr.window.html b/Tests/LibWeb/Text/input/wpt-import/webstorage/storage_local_setitem_quotaexceedederr.window.html
new file mode 100644
index 00000000000..f8050e7da1e
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/webstorage/storage_local_setitem_quotaexceedederr.window.html
@@ -0,0 +1,22 @@
+<script src="../../include.js"></script>
+<script>
+    // FIXME: This should be an import of WPT from webstorage/storage_local_setitem_quotaexceedederr.window.html
+    test(() => {
+        localStorage.clear();
+
+        var index = 0;
+        var key = "name";
+        var val = "x".repeat(1024);
+
+        try {
+            while (true) {
+                index++;
+                localStorage.setItem("" + key + index, "" + val + index);
+            }
+        } catch (e) {
+            println(e);
+        }
+
+        localStorage.clear();
+    });
+</script>
diff --git a/Tests/LibWeb/Text/input/wpt-import/webstorage/storage_session_setitem_quotaexceedederr.window.html b/Tests/LibWeb/Text/input/wpt-import/webstorage/storage_session_setitem_quotaexceedederr.window.html
new file mode 100644
index 00000000000..d220c9b99b5
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/webstorage/storage_session_setitem_quotaexceedederr.window.html
@@ -0,0 +1,22 @@
+<script src="../../include.js"></script>
+<script>
+    // FIXME: This should be an import of WPT from webstorage/storage_session_setitem_quotaexceedederr.window.html
+    test(() => {
+        sessionStorage.clear();
+
+        var index = 0;
+        var key = "name";
+        var val = "x".repeat(1024);
+
+        try {
+            while (true) {
+                index++;
+                sessionStorage.setItem("" + key + index, "" + val + index);
+            }
+        } catch (e) {
+            println(e);
+        }
+
+        sessionStorage.clear();
+    });
+</script>