diff --git a/doc/cc65.sgml b/doc/cc65.sgml
index efe48b61b..53b9d0773 100644
--- a/doc/cc65.sgml
+++ b/doc/cc65.sgml
@@ -1681,6 +1681,16 @@ void somefunc2(int, char *);
   </verb></tscreen>
 
 
+<sect1><tt>#pragma once</tt><label id="pragma-once"><p>
+
+  This pragma is used to prevent multiple inclusion of a header file.
+  If this pragma is preprocessed in a file, any posterior
+  <tt>#include</tt> which targets the current file will be ignored.
+
+  Two files are considered to be the same by this directive if they
+  share the same absolute path. In the case of symbolic links,
+  the canonical, resolved path is considered instead.
+
 
 <sect>Register variables<label id="register-vars"><p>
 
diff --git a/src/cc65/input.c b/src/cc65/input.c
index fcf7f32f3..678d5645f 100644
--- a/src/cc65/input.c
+++ b/src/cc65/input.c
@@ -45,6 +45,7 @@
 #include "print.h"
 #include "strbuf.h"
 #include "xmalloc.h"
+#include "pathutil.h"
 
 /* cc65 */
 #include "codegen.h"
@@ -296,10 +297,11 @@ void OpenMainFile (const char* Name)
 
 
 
-void OpenIncludeFile (const char* Name, InputType IT)
+void OpenIncludeFile (const char* Name, InputType IT, StringPool *FilesToIgnore)
 /* Open an include file and insert it into the tables. */
 {
     char*  N;
+    char*  M;
     FILE*  F;
     IFile* IF;
     AFile* AF;
@@ -317,6 +319,23 @@ void OpenIncludeFile (const char* Name, InputType IT)
         return;
     }
 
+    /* Resolve real path of file in case of a symlink */
+    M = FindRealPath(N);
+    if (M == 0) {
+        PPError ("Cannot resolve absolute path of '%s'", N);
+        xfree (N);
+        return;
+    }
+
+    if (SP_LookupStr(FilesToIgnore, M) != 0) {
+        /* This file should not be included. */
+        xfree (M);
+        xfree (N);
+        return;
+    }
+
+    xfree (M);
+
     /* Search the list of all input files for this file. If we don't find
     ** it, create a new IFile object.
     */
diff --git a/src/cc65/input.h b/src/cc65/input.h
index 9a5a76949..0053d04af 100644
--- a/src/cc65/input.h
+++ b/src/cc65/input.h
@@ -43,6 +43,7 @@
 /* common */
 #include "coll.h"
 #include "strbuf.h"
+#include "strpool.h"
 
 
 
@@ -83,8 +84,10 @@ extern char NextC;
 void OpenMainFile (const char* Name);
 /* Open the main file. Will call Fatal() in case of failures. */
 
-void OpenIncludeFile (const char* Name, InputType IT);
-/* Open an include file and insert it into the tables. */
+void OpenIncludeFile (const char* Name, InputType IT, StringPool* FilesToIgnore);
+/* Open an include file and insert it into the tables.
+** Does nothing if the resolved file is present in the pool.
+*/
 
 void CloseIncludeFile (void);
 /* Close an include file and switch to the higher level file. Set Input to
diff --git a/src/cc65/preproc.c b/src/cc65/preproc.c
index 66cbb2a9d..e93b5abbe 100644
--- a/src/cc65/preproc.c
+++ b/src/cc65/preproc.c
@@ -44,6 +44,9 @@
 #include "inline.h"
 #include "print.h"
 #include "xmalloc.h"
+#include "strpool.h"
+#include "abend.h"
+#include "pathutil.h"
 
 /* cc65 */
 #include "codegen.h"
@@ -113,6 +116,8 @@ static StrBuf* PLine;   /* Buffer for macro expansion */
 static StrBuf* MLine;   /* Buffer for macro expansion in #pragma */
 static StrBuf* OLine;   /* Buffer for #pragma output */
 
+static StringPool* PragmaOnceSeenFiles;
+
 /* Newlines to be added to preprocessed text */
 static unsigned PendingNewLines;
 static unsigned ContinuedLines;
@@ -2804,7 +2809,6 @@ static int DoIfDef (int skip, int flag)
 }
 
 
-
 static void DoInclude (void)
 /* Open an include file. */
 {
@@ -2854,8 +2858,8 @@ static void DoInclude (void)
         NextChar ();
         /* Check for extra tokens following the filename */
         CheckExtraTokens ("include");
-        /* Open the include file */
-        OpenIncludeFile (SB_GetConstBuf (&Filename), IT);
+        /* Open the include file, if it is not marked with #pragma once */
+        OpenIncludeFile (SB_GetConstBuf (&Filename), IT, PragmaOnceSeenFiles);
     } else {
         /* No terminator found */
         PPError ("#include expects \"FILENAME\" or <FILENAME>");
@@ -2963,14 +2967,28 @@ static void DoLine (void)
     MLine = InitLine (MLine);
 }
 
+static void DoPragmaOnce (void)
+/* Marks the current file as seen by #pragma once. */
+{
+    const char * const Filename = GetCurrentFilename ();
 
+    char * const FullPath = FindRealPath (Filename);
+
+    if (FullPath == NULL) {
+        AbEnd ("Failed to find the real path for the file %s", Filename);
+    }
+
+    SP_AddStr (PragmaOnceSeenFiles, FullPath);
+
+    free (FullPath);
+}
 
 static void DoPragma (void)
 /* Handle a #pragma line by converting the #pragma preprocessor directive into
 ** the _Pragma() compiler operator.
 */
 {
-    StrBuf* PragmaLine = OLine;
+    StrBuf* const PragmaLine = OLine;
 
     PRECONDITION (PragmaLine != 0);
 
@@ -2981,11 +2999,16 @@ static void DoPragma (void)
     SB_Clear (MLine);
     PreprocessDirective (Line, MLine, MSM_NONE);
 
-    /* Convert #pragma to _Pragma () */
-    SB_AppendStr (PragmaLine, "_Pragma (");
-    SB_Reset (MLine);
-    Stringize (MLine, PragmaLine);
-    SB_AppendChar (PragmaLine, ')');
+    if (SB_CompareStr(MLine, "once") == 0) {
+        DoPragmaOnce ();
+    }
+    else {
+        /* Convert #pragma to _Pragma () */
+        SB_AppendStr (PragmaLine, "_Pragma (");
+        SB_Reset (MLine);
+        Stringize (MLine, PragmaLine);
+        SB_AppendChar (PragmaLine, ')');
+    }
 
     /* End this line */
     SB_SetIndex (PragmaLine, SB_GetLen (PragmaLine));
@@ -3157,6 +3180,7 @@ static int ParseDirectives (unsigned ModeFlags)
                         if (!PPSkip) {
                             if ((ModeFlags & MSM_IN_ARG_LIST) == 0) {
                                 DoPragma ();
+
                                 return Whitespace;
                             } else {
                                 PPError ("Embedded #pragma directive within macro arguments is unsupported");
@@ -3348,6 +3372,9 @@ void InitPreprocess (void)
     /* Create the output buffers */
     MLine = NewStrBuf ();
     PLine = NewStrBuf ();
+
+    /* 64 is a sensible number of slots for the hash table */
+    PragmaOnceSeenFiles = NewStringPool(64);
 }
 
 
@@ -3358,6 +3385,7 @@ void DonePreprocess (void)
     /* Done with the output buffers */
     SB_Done (MLine);
     SB_Done (PLine);
+    FreeStringPool(PragmaOnceSeenFiles);
 }
 
 
diff --git a/src/common.vcxproj b/src/common.vcxproj
index 6098c98a0..5a6855208 100644
--- a/src/common.vcxproj
+++ b/src/common.vcxproj
@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup Label="ProjectConfigurations">
     <ProjectConfiguration Include="Debug|Win32">
@@ -110,6 +110,7 @@
     <ClInclude Include="common\objdefs.h" />
     <ClInclude Include="common\optdefs.h" />
     <ClInclude Include="common\print.h" />
+    <ClInclude Include="common\pathutil.h" />
     <ClInclude Include="common\scopedefs.h" />
     <ClInclude Include="common\searchpath.h" />
     <ClInclude Include="common\segdefs.h" />
@@ -155,6 +156,7 @@
     <ClCompile Include="common\matchpat.c" />
     <ClCompile Include="common\mmodel.c" />
     <ClCompile Include="common\print.c" />
+    <ClCompile Include="common\pathutil.c" />
     <ClCompile Include="common\searchpath.c" />
     <ClCompile Include="common\segnames.c" />
     <ClCompile Include="common\shift.c" />
@@ -171,4 +173,4 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
-</Project>
\ No newline at end of file
+</Project>
diff --git a/src/common/pathutil.c b/src/common/pathutil.c
new file mode 100644
index 000000000..a3b159a59
--- /dev/null
+++ b/src/common/pathutil.c
@@ -0,0 +1,119 @@
+/*****************************************************************************/
+/*                                                                           */
+/*                                pathutil.c                                 */
+/*                         Path manipulation utilities                       */
+/*                                                                           */
+/*                                                                           */
+/*                                                                           */
+/* (C) 2003-2008 Ullrich von Bassewitz                                       */
+/*               Roemerstrasse 52                                            */
+/*               D-70794 Filderstadt                                         */
+/* EMail:        uz@cc65.org                                                 */
+/*                                                                           */
+/*                                                                           */
+/* This software is provided 'as-is', without any expressed or implied       */
+/* warranty.  In no event will the authors be held liable for any damages    */
+/* arising from the use of this software.                                    */
+/*                                                                           */
+/* Permission is granted to anyone to use this software for any purpose,     */
+/* including commercial applications, and to alter it and redistribute it    */
+/* freely, subject to the following restrictions:                            */
+/*                                                                           */
+/* 1. The origin of this software must not be misrepresented; you must not   */
+/*    claim that you wrote the original software. If you use this software   */
+/*    in a product, an acknowledgment in the product documentation would be  */
+/*    appreciated but is not required.                                       */
+/* 2. Altered source versions must be plainly marked as such, and must not   */
+/*    be misrepresented as being the original software.                      */
+/* 3. This notice may not be removed or altered from any source              */
+/*    distribution.                                                          */
+/*                                                                           */
+/*****************************************************************************/
+
+#if defined(_WIN32)
+
+#if !defined(_WIN32_WINNT) && !defined(NTDDI_VERSION)
+
+/* Set minimum windows version for GetFinalPathNameByHandleA */
+/* NTDDI_VISTA */
+#define NTDDI_VERSION 0x06000000
+
+/* _WIN32_WINNT_VISTA */
+#define _WIN32_WINNT 0x600
+
+#endif
+
+#include "xmalloc.h"
+#include <windows.h>
+#include <fileapi.h>
+
+#endif
+
+#include <stdlib.h>
+
+
+
+/*****************************************************************************/
+/*                                   code                                    */
+/*****************************************************************************/
+
+
+
+#if defined(_WIN32)
+
+char *FindRealPath (const char *Path)
+/*
+** Returns a malloced buffer containing the canonical path of the given path.
+** If the path points to a non-existent file, or if any error occurs, NULL is returned.
+** If the path points to a symlink, the resolved symlink path is returned.
+** Note: The returned path's separator is system specific.
+*/
+{
+
+    HANDLE Handle = CreateFileA (Path,
+                                 FILE_READ_ATTRIBUTES,
+                                 FILE_SHARE_READ |
+                                 FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+                                 NULL,
+                                 OPEN_EXISTING,
+                                 FILE_FLAG_BACKUP_SEMANTICS,
+                                 NULL);
+
+    if (Handle == INVALID_HANDLE_VALUE) {
+        return NULL;
+    }
+
+    size_t BufferSize = MAX_PATH + 10;
+    char* Buffer = xmalloc (BufferSize);
+
+    DWORD Status = GetFinalPathNameByHandleA (Handle,
+                                              Buffer,
+                                              BufferSize,
+                                              FILE_NAME_NORMALIZED
+                                              | VOLUME_NAME_DOS);
+
+    if (Status == 0) {
+        xfree (Buffer);
+        CloseHandle (Handle);
+        return NULL;
+    }
+
+    CloseHandle (Handle);
+
+    return Buffer;
+}
+
+#else
+
+char* FindRealPath (const char* path)
+/*
+** Returns a malloced buffer containing the canonical path of the given path.
+** If the path points to a non-existent file, or if any error occurs, NULL is returned.
+** If the path points to a symlink, the resolved symlink path is returned.
+** Note: The returned path's separator is system specific.
+*/
+{
+    return realpath (path, NULL);
+}
+
+#endif
diff --git a/src/common/pathutil.h b/src/common/pathutil.h
new file mode 100644
index 000000000..2e2154102
--- /dev/null
+++ b/src/common/pathutil.h
@@ -0,0 +1,55 @@
+/*****************************************************************************/
+/*                                                                           */
+/*                                pathutil.h                                 */
+/*                         Path manipulation utilities                       */
+/*                                                                           */
+/*                                                                           */
+/*                                                                           */
+/* (C) 2003-2008 Ullrich von Bassewitz                                       */
+/*               Roemerstrasse 52                                            */
+/*               D-70794 Filderstadt                                         */
+/* EMail:        uz@cc65.org                                                 */
+/*                                                                           */
+/*                                                                           */
+/* This software is provided 'as-is', without any expressed or implied       */
+/* warranty.  In no event will the authors be held liable for any damages    */
+/* arising from the use of this software.                                    */
+/*                                                                           */
+/* Permission is granted to anyone to use this software for any purpose,     */
+/* including commercial applications, and to alter it and redistribute it    */
+/* freely, subject to the following restrictions:                            */
+/*                                                                           */
+/* 1. The origin of this software must not be misrepresented; you must not   */
+/*    claim that you wrote the original software. If you use this software   */
+/*    in a product, an acknowledgment in the product documentation would be  */
+/*    appreciated but is not required.                                       */
+/* 2. Altered source versions must be plainly marked as such, and must not   */
+/*    be misrepresented as being the original software.                      */
+/* 3. This notice may not be removed or altered from any source              */
+/*    distribution.                                                          */
+/*                                                                           */
+/*****************************************************************************/
+
+
+
+#ifndef PATHUTIL_H
+#define PATHUTIL_H
+
+
+/*****************************************************************************/
+/*                                     Code                                  */
+/*****************************************************************************/
+
+
+char *FindRealPath (const char *path);
+/*
+** Returns a malloced buffer containing the canonical path of the given path.
+** If the path points to a non-existent file, or if any error occurs, NULL is returned.
+** If the path points to a symlink, the resolved symlink path is returned.
+** Note: The returned path's separator is system specific.
+*/
+
+
+/* End of pathutil.h */
+
+#endif
diff --git a/src/common/searchpath.c b/src/common/searchpath.c
index 3628dab5c..592c10ccb 100644
--- a/src/common/searchpath.c
+++ b/src/common/searchpath.c
@@ -377,6 +377,7 @@ char* SearchFile (const SearchPaths* P, const char* File)
         SB_AppendStr (&PathName, File);
         SB_Terminate (&PathName);
 
+
         /* Check if this file exists */
         if (access (SB_GetBuf (&PathName), 0) == 0) {
             /* The file exists, we're done */
diff --git a/src/common/strpool.c b/src/common/strpool.c
index 244681afd..e7fec1208 100644
--- a/src/common/strpool.c
+++ b/src/common/strpool.c
@@ -281,3 +281,22 @@ unsigned SP_GetCount (const StringPool* P)
 {
     return CollCount (&P->Entries);
 }
+
+unsigned SP_Lookup(StringPool *P, const StrBuf *S)
+/*
+** Determine whether the given string is in the pool.
+** Returns 1 if the string is in the pool, 0 otherwise.
+*/
+{
+    return HT_Find (&P->Tab, S) != 0;
+}
+
+unsigned SP_LookupStr(StringPool *P, const char *S)
+/*
+** Determine whether the given string is in the pool.
+** Returns 1 if the string is in the pool, 0 otherwise.
+*/
+{
+    StrBuf Buf;
+    return SP_Lookup (P, SB_InitFromString (&Buf, S));
+}
diff --git a/src/common/strpool.h b/src/common/strpool.h
index 8a6a8faee..fefab27e1 100644
--- a/src/common/strpool.h
+++ b/src/common/strpool.h
@@ -84,7 +84,7 @@ const StrBuf* SP_Get (const StringPool* P, unsigned Index);
 
 unsigned SP_Add (StringPool* P, const StrBuf* S);
 /* Add a string buffer to the buffer and return the index. If the string does
-** already exist in the pool, SP_AddBuf will just return the index of the
+** already exist in the pool, SP_Add will just return the index of the
 ** existing string.
 */
 
@@ -96,6 +96,18 @@ unsigned SP_AddStr (StringPool* P, const char* S);
 unsigned SP_GetCount (const StringPool* P);
 /* Return the number of strings in the pool */
 
+unsigned SP_Lookup(StringPool *P, const StrBuf *S);
+/*
+** Determine whether the given string is in the pool.
+** Returns 1 if the string is in the pool, 0 otherwise.
+*/
+
+unsigned SP_LookupStr(StringPool *P, const char *S);
+/*
+** Determine whether the given string is in the pool.
+** Returns 1 if the string is in the pool, 0 otherwise.
+*/
+
 
 
 /* End of strpool.h */
diff --git a/test/val/pragma-once-sample-2.h b/test/val/pragma-once-sample-2.h
new file mode 100644
index 000000000..86fdc2108
--- /dev/null
+++ b/test/val/pragma-once-sample-2.h
@@ -0,0 +1,8 @@
+/*
+** !!DESCRIPTION!! Simple #pragma once directive tests
+** !!ORIGIN!!      cc65 regression tests
+** !!LICENCE!!     Public Domain
+*/
+
+#include "pragma-once-sample.h";
+
diff --git a/test/val/pragma-once-sample.h b/test/val/pragma-once-sample.h
new file mode 100644
index 000000000..477c7c8bd
--- /dev/null
+++ b/test/val/pragma-once-sample.h
@@ -0,0 +1,21 @@
+/*
+** !!DESCRIPTION!! Simple #pragma once directive tests
+** !!ORIGIN!!      cc65 regression tests
+** !!LICENCE!!     Public Domain
+*/
+
+#ifdef FILE_INCLUDED
+
+#error "This file should not have been included twice"
+#define INCLUDED_TWICE
+
+#else
+
+#define FILE_INCLUDED
+
+#endif
+
+
+/* a pragma once directive should work regardless of where it is located in
+   the file, as long as it is seen by the preprocessor */
+#pragma once
diff --git a/test/val/pragma-once-test.c b/test/val/pragma-once-test.c
new file mode 100644
index 000000000..0816c7698
--- /dev/null
+++ b/test/val/pragma-once-test.c
@@ -0,0 +1,27 @@
+/*
+** !!DESCRIPTION!! Simple #pragma once directive tests
+** !!ORIGIN!!      cc65 regression tests
+** !!LICENCE!!     Public Domain
+*/
+
+#pragma once
+
+#include "pragma-once-sample-2.h"
+#include "pragma-once-sample-2.h"
+#include "pragma-once-sample.h"
+#include "pragma-once-sample.h"
+
+
+#include <stdio.h>
+
+
+int main() {
+
+#ifdef INCLUDED_TWICE
+    printf("pragma-once-sample.h included more than once\n");
+    return 1;
+#else
+    printf("pragma-once-sample included once\n");
+    return 0;
+#endif
+}