diff --git a/Applications/SystemMonitor/ProcessMemoryMapWidget.h b/Applications/SystemMonitor/ProcessMemoryMapWidget.h
index 7ee822b673..31741a9b55 100644
--- a/Applications/SystemMonitor/ProcessMemoryMapWidget.h
+++ b/Applications/SystemMonitor/ProcessMemoryMapWidget.h
@@ -28,9 +28,6 @@
 
 #include <LibGUI/Widget.h>
 
-namespace Core {
-class Timer;
-}
 namespace GUI {
 class JsonArrayModel;
 class TableView;
diff --git a/Applications/SystemMonitor/ProcessStacksWidget.h b/Applications/SystemMonitor/ProcessStacksWidget.h
index e0e4c59062..1dc3c4bbaf 100644
--- a/Applications/SystemMonitor/ProcessStacksWidget.h
+++ b/Applications/SystemMonitor/ProcessStacksWidget.h
@@ -29,10 +29,6 @@
 #include <LibGUI/TextEditor.h>
 #include <LibGUI/Widget.h>
 
-namespace Core {
-class Timer;
-}
-
 class ProcessStacksWidget final : public GUI::Widget {
     C_OBJECT(ProcessStacksWidget)
 public:
diff --git a/DevTools/HackStudio/ProcessStateWidget.h b/DevTools/HackStudio/ProcessStateWidget.h
index e1e49a170a..97888371bf 100644
--- a/DevTools/HackStudio/ProcessStateWidget.h
+++ b/DevTools/HackStudio/ProcessStateWidget.h
@@ -28,9 +28,6 @@
 
 #include <LibGUI/Widget.h>
 
-namespace Core {
-class Timer;
-}
 namespace GUI {
 class Label;
 }
diff --git a/Libraries/LibGUI/Event.h b/Libraries/LibGUI/Event.h
index 17e71783a0..fd378b5200 100644
--- a/Libraries/LibGUI/Event.h
+++ b/Libraries/LibGUI/Event.h
@@ -32,10 +32,6 @@
 #include <LibGfx/Rect.h>
 #include <LibGUI/WindowType.h>
 
-namespace Core {
-class MimeData;
-}
-
 namespace GUI {
 
 class Event : public Core::Event {
diff --git a/Libraries/LibHTML/DOM/HTMLBlinkElement.h b/Libraries/LibHTML/DOM/HTMLBlinkElement.h
index 8e9594bbf3..3cb5b350d4 100644
--- a/Libraries/LibHTML/DOM/HTMLBlinkElement.h
+++ b/Libraries/LibHTML/DOM/HTMLBlinkElement.h
@@ -26,12 +26,9 @@
 
 #pragma once
 
+#include <LibCore/Forward.h>
 #include <LibHTML/DOM/HTMLElement.h>
 
-namespace Core {
-class Timer;
-}
-
 class HTMLBlinkElement : public HTMLElement {
 public:
     HTMLBlinkElement(Document&, const String& tag_name);
diff --git a/Servers/LookupServer/LookupServer.h b/Servers/LookupServer/LookupServer.h
index b547ec3ef7..4666e0904b 100644
--- a/Servers/LookupServer/LookupServer.h
+++ b/Servers/LookupServer/LookupServer.h
@@ -31,11 +31,6 @@
 #include <AK/HashMap.h>
 #include <LibCore/Object.h>
 
-namespace Core {
-class LocalSocket;
-class LocalServer;
-}
-
 class DNSAnswer;
 
 class LookupServer final : public Core::Object {
diff --git a/Servers/ProtocolServer/HttpDownload.h b/Servers/ProtocolServer/HttpDownload.h
index 246f18e26f..8ec1809e97 100644
--- a/Servers/ProtocolServer/HttpDownload.h
+++ b/Servers/ProtocolServer/HttpDownload.h
@@ -27,12 +27,9 @@
 #pragma once
 
 #include <AK/Badge.h>
+#include <LibCore/Forward.h>
 #include <ProtocolServer/Download.h>
 
-namespace Core {
-class CoreHttpJob;
-}
-
 class HttpProtocol;
 
 class HttpDownload final : public Download {
diff --git a/Servers/WebServer/Client.h b/Servers/WebServer/Client.h
index bf43ffdfbb..db2f727057 100644
--- a/Servers/WebServer/Client.h
+++ b/Servers/WebServer/Client.h
@@ -29,10 +29,6 @@
 #include <LibCore/Object.h>
 #include <LibCore/TCPSocket.h>
 
-namespace Core {
-class HttpRequest;
-}
-
 namespace WebServer {
 
 class Client final : public Core::Object {