diff --git a/Kernel/Devices/FloppyDiskDevice.cpp b/Kernel/Devices/FloppyDiskDevice.cpp
index 5d7902160f..79d84c670e 100644
--- a/Kernel/Devices/FloppyDiskDevice.cpp
+++ b/Kernel/Devices/FloppyDiskDevice.cpp
@@ -24,10 +24,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include <Kernel/Arch/i386/PIT.h>
 #include <Kernel/Devices/FloppyDiskDevice.h>
-#include <Kernel/FileSystem/ProcFS.h>
-#include <Kernel/Process.h>
 #include <Kernel/VM/MemoryManager.h>
 #include <LibBareMetal/IO.h>
 
diff --git a/Kernel/Devices/KeyboardDevice.cpp b/Kernel/Devices/KeyboardDevice.cpp
index 2c7bb907a7..8b9071b708 100644
--- a/Kernel/Devices/KeyboardDevice.cpp
+++ b/Kernel/Devices/KeyboardDevice.cpp
@@ -25,6 +25,7 @@
  */
 
 #include <AK/Assertions.h>
+#include <AK/ByteBuffer.h>
 #include <AK/Types.h>
 #include <Kernel/Arch/i386/CPU.h>
 #include <Kernel/Arch/i386/PIC.h>
diff --git a/Kernel/FileSystem/DiskBackedFileSystem.cpp b/Kernel/FileSystem/DiskBackedFileSystem.cpp
index 05f62c09fc..62b61285d4 100644
--- a/Kernel/FileSystem/DiskBackedFileSystem.cpp
+++ b/Kernel/FileSystem/DiskBackedFileSystem.cpp
@@ -25,6 +25,7 @@
  */
 
 #include <Kernel/Arch/i386/CPU.h>
+#include <Kernel/Devices/BlockDevice.h>
 #include <Kernel/FileSystem/DiskBackedFileSystem.h>
 #include <Kernel/FileSystem/FileDescription.h>
 #include <Kernel/KBuffer.h>
diff --git a/Kernel/FileSystem/DiskBackedFileSystem.h b/Kernel/FileSystem/DiskBackedFileSystem.h
index e6b1553f56..a5909eaf39 100644
--- a/Kernel/FileSystem/DiskBackedFileSystem.h
+++ b/Kernel/FileSystem/DiskBackedFileSystem.h
@@ -26,13 +26,11 @@
 
 #pragma once
 
-#include "FileSystem.h"
-#include <AK/ByteBuffer.h>
+#include <Kernel/FileSystem/FileSystem.h>
+#include <Kernel/Forward.h>
 
 namespace Kernel {
 
-class DiskCache;
-
 class DiskBackedFS : public FS {
 public:
     virtual ~DiskBackedFS() override;
diff --git a/Kernel/FileSystem/Ext2FileSystem.cpp b/Kernel/FileSystem/Ext2FileSystem.cpp
index 9433b3e5bf..8778c2ca05 100644
--- a/Kernel/FileSystem/Ext2FileSystem.cpp
+++ b/Kernel/FileSystem/Ext2FileSystem.cpp
@@ -26,7 +26,9 @@
 
 #include <AK/Bitmap.h>
 #include <AK/BufferStream.h>
+#include <AK/HashMap.h>
 #include <AK/StdLibExtras.h>
+#include <Kernel/Devices/BlockDevice.h>
 #include <Kernel/FileSystem/Ext2FileSystem.h>
 #include <Kernel/FileSystem/FileDescription.h>
 #include <Kernel/FileSystem/ext2_fs.h>
diff --git a/Kernel/FileSystem/File.h b/Kernel/FileSystem/File.h
index c812b9b2ca..3779ef8510 100644
--- a/Kernel/FileSystem/File.h
+++ b/Kernel/FileSystem/File.h
@@ -30,16 +30,13 @@
 #include <AK/RefCounted.h>
 #include <AK/String.h>
 #include <AK/Types.h>
+#include <Kernel/Forward.h>
 #include <Kernel/KResult.h>
 #include <Kernel/UnixTypes.h>
 #include <LibBareMetal/Memory/VirtualAddress.h>
 
 namespace Kernel {
 
-class FileDescription;
-class Process;
-class Region;
-
 // File is the base class for anything that can be referenced by a FileDescription.
 //
 // The most important functions in File are:
diff --git a/Kernel/FileSystem/FileSystem.h b/Kernel/FileSystem/FileSystem.h
index 14ee89a6ba..32e9fbf47e 100644
--- a/Kernel/FileSystem/FileSystem.h
+++ b/Kernel/FileSystem/FileSystem.h
@@ -26,17 +26,10 @@
 
 #pragma once
 
-#include <AK/ByteBuffer.h>
-#include <AK/Function.h>
-#include <AK/HashMap.h>
-#include <AK/OwnPtr.h>
 #include <AK/RefCounted.h>
 #include <AK/RefPtr.h>
 #include <AK/String.h>
-#include <AK/WeakPtr.h>
-#include <Kernel/Devices/BlockDevice.h>
 #include <Kernel/FileSystem/InodeIdentifier.h>
-#include <Kernel/FileSystem/InodeMetadata.h>
 #include <Kernel/KResult.h>
 #include <Kernel/Lock.h>
 #include <Kernel/UnixTypes.h>
diff --git a/Kernel/FileSystem/Inode.h b/Kernel/FileSystem/Inode.h
index 1289cc2ca4..4c4bd1c619 100644
--- a/Kernel/FileSystem/Inode.h
+++ b/Kernel/FileSystem/Inode.h
@@ -34,17 +34,12 @@
 #include <Kernel/FileSystem/FileSystem.h>
 #include <Kernel/FileSystem/InodeIdentifier.h>
 #include <Kernel/FileSystem/InodeMetadata.h>
+#include <Kernel/Forward.h>
 #include <Kernel/KResult.h>
 #include <Kernel/Lock.h>
 
 namespace Kernel {
 
-class FileDescription;
-class InodeVMObject;
-class InodeWatcher;
-class LocalSocket;
-class Custody;
-
 class Inode : public RefCounted<Inode>
     , public Weakable<Inode>
     , public InlineLinkedListNode<Inode> {
diff --git a/Kernel/FileSystem/ProcFS.cpp b/Kernel/FileSystem/ProcFS.cpp
index 1d4dde41e5..fc623d8cc9 100644
--- a/Kernel/FileSystem/ProcFS.cpp
+++ b/Kernel/FileSystem/ProcFS.cpp
@@ -33,6 +33,7 @@
 #include <AK/JsonObjectSerializer.h>
 #include <AK/JsonValue.h>
 #include <Kernel/Arch/i386/CPU.h>
+#include <Kernel/Devices/BlockDevice.h>
 #include <Kernel/FileSystem/Custody.h>
 #include <Kernel/FileSystem/DiskBackedFileSystem.h>
 #include <Kernel/FileSystem/FileDescription.h>
diff --git a/Kernel/FileSystem/ProcFS.h b/Kernel/FileSystem/ProcFS.h
index e482a1a734..3732ba4c75 100644
--- a/Kernel/FileSystem/ProcFS.h
+++ b/Kernel/FileSystem/ProcFS.h
@@ -26,6 +26,7 @@
 
 #pragma once
 
+#include <AK/HashMap.h>
 #include <AK/Types.h>
 #include <Kernel/FileSystem/FileSystem.h>
 #include <Kernel/FileSystem/Inode.h>
diff --git a/Kernel/FileSystem/TmpFS.h b/Kernel/FileSystem/TmpFS.h
index a7c67f90ab..65c910ba13 100644
--- a/Kernel/FileSystem/TmpFS.h
+++ b/Kernel/FileSystem/TmpFS.h
@@ -26,6 +26,7 @@
 
 #pragma once
 
+#include <AK/HashMap.h>
 #include <AK/Optional.h>
 #include <Kernel/FileSystem/FileSystem.h>
 #include <Kernel/FileSystem/Inode.h>
diff --git a/Kernel/FileSystem/VirtualFileSystem.cpp b/Kernel/FileSystem/VirtualFileSystem.cpp
index 5069e9ca56..09da750d90 100644
--- a/Kernel/FileSystem/VirtualFileSystem.cpp
+++ b/Kernel/FileSystem/VirtualFileSystem.cpp
@@ -26,7 +26,7 @@
 
 #include <AK/FileSystemPath.h>
 #include <AK/StringBuilder.h>
-#include <Kernel/Devices/CharacterDevice.h>
+#include <Kernel/Devices/BlockDevice.h>
 #include <Kernel/FileSystem/Custody.h>
 #include <Kernel/FileSystem/DiskBackedFileSystem.h>
 #include <Kernel/FileSystem/FileDescription.h>
diff --git a/Kernel/Forward.h b/Kernel/Forward.h
new file mode 100644
index 0000000000..d1e3fd9187
--- /dev/null
+++ b/Kernel/Forward.h
@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+namespace Kernel {
+
+class BlockDevice;
+class CharacterDevice;
+class Custody;
+class Device;
+class DiskCache;
+class DoubleBuffer;
+class File;
+class FileDescription;
+class IPv4Socket;
+class Inode;
+class InodeIdentifier;
+class InodeVMObject;
+class InodeWatcher;
+class KBuffer;
+class KResult;
+class LocalSocket;
+class PageDirectory;
+class PhysicalPage;
+class PhysicalRegion;
+class Process;
+class ProcessInspectionHandle;
+class ProcessTracer;
+class Range;
+class RangeAllocator;
+class Region;
+class Scheduler;
+class SharedBuffer;
+class Socket;
+class TCPSocket;
+class Thread;
+class UDPSocket;
+class VMObject;
+class WaitQueue;
+
+template<typename T>
+class KResultOr;
+
+}
diff --git a/Kernel/KBuffer.h b/Kernel/KBuffer.h
index 91cdc09b64..725ae9df43 100644
--- a/Kernel/KBuffer.h
+++ b/Kernel/KBuffer.h
@@ -37,6 +37,7 @@
 // severely limited kmalloc heap.
 
 #include <AK/Assertions.h>
+#include <AK/ByteBuffer.h>
 #include <AK/LogStream.h>
 #include <Kernel/VM/MemoryManager.h>
 #include <Kernel/VM/Region.h>
diff --git a/Kernel/Lock.h b/Kernel/Lock.h
index 8f1ed86b95..c48104deb8 100644
--- a/Kernel/Lock.h
+++ b/Kernel/Lock.h
@@ -30,12 +30,11 @@
 #include <AK/Atomic.h>
 #include <AK/Types.h>
 #include <Kernel/Arch/i386/CPU.h>
-#include <Kernel/Scheduler.h>
+#include <Kernel/Forward.h>
 #include <Kernel/WaitQueue.h>
 
 namespace Kernel {
 
-class Thread;
 extern Thread* current;
 
 class Lock {
diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
index d947efb7f5..c5287a5932 100644
--- a/Kernel/Process.cpp
+++ b/Kernel/Process.cpp
@@ -33,6 +33,7 @@
 #include <AK/Types.h>
 #include <Kernel/Arch/i386/CPU.h>
 #include <Kernel/Arch/i386/PIT.h>
+#include <Kernel/Devices/BlockDevice.h>
 #include <Kernel/Devices/KeyboardDevice.h>
 #include <Kernel/Devices/NullDevice.h>
 #include <Kernel/Devices/PCSpeaker.h>
diff --git a/Kernel/Process.h b/Kernel/Process.h
index 46520de607..27ac4f3edb 100644
--- a/Kernel/Process.h
+++ b/Kernel/Process.h
@@ -34,6 +34,7 @@
 #include <AK/WeakPtr.h>
 #include <AK/Weakable.h>
 #include <Kernel/FileSystem/VirtualFileSystem.h>
+#include <Kernel/Forward.h>
 #include <Kernel/Lock.h>
 #include <Kernel/PerformanceEventBuffer.h>
 #include <Kernel/Syscall.h>
@@ -47,14 +48,6 @@ class ELFLoader;
 
 namespace Kernel {
 
-class FileDescription;
-class KBuffer;
-class PageDirectory;
-class Region;
-class VMObject;
-class ProcessTracer;
-class SharedBuffer;
-
 timeval kgettimeofday();
 void kgettimeofday(timeval&);
 
diff --git a/Kernel/Thread.h b/Kernel/Thread.h
index 400281be9c..0941bcf247 100644
--- a/Kernel/Thread.h
+++ b/Kernel/Thread.h
@@ -36,6 +36,7 @@
 #include <AK/String.h>
 #include <AK/Vector.h>
 #include <Kernel/Arch/i386/CPU.h>
+#include <Kernel/Forward.h>
 #include <Kernel/KResult.h>
 #include <Kernel/Scheduler.h>
 #include <Kernel/UnixTypes.h>
@@ -43,13 +44,6 @@
 
 namespace Kernel {
 
-class Alarm;
-class FileDescription;
-class Process;
-class ProcessInspectionHandle;
-class Region;
-class WaitQueue;
-
 enum class ShouldUnblockThread {
     No = 0,
     Yes
diff --git a/Kernel/VM/MemoryManager.h b/Kernel/VM/MemoryManager.h
index 2ab5b3b65a..98114e1fe4 100644
--- a/Kernel/VM/MemoryManager.h
+++ b/Kernel/VM/MemoryManager.h
@@ -26,23 +26,17 @@
 
 #pragma once
 
-#include <AK/Badge.h>
-#include <AK/Bitmap.h>
-#include <AK/ByteBuffer.h>
 #include <AK/HashTable.h>
 #include <AK/NonnullRefPtrVector.h>
 #include <AK/String.h>
-#include <AK/Types.h>
 #include <Kernel/Arch/i386/CPU.h>
-#include <Kernel/FileSystem/InodeIdentifier.h>
+#include <Kernel/Forward.h>
 #include <Kernel/VM/PhysicalPage.h>
 #include <Kernel/VM/Region.h>
 #include <Kernel/VM/VMObject.h>
 
 namespace Kernel {
 
-class PhysicalRegion;
-
 #define PAGE_ROUND_UP(x) ((((u32)(x)) + PAGE_SIZE - 1) & (~(PAGE_SIZE - 1)))
 
 template<typename T>