diff --git a/library/include/string.h b/library/include/string.h
index babde29..57d5974 100644
--- a/library/include/string.h
+++ b/library/include/string.h
@@ -62,6 +62,7 @@ extern int strcmp(const char *s1, const char * s2);
 extern int strncmp(const char *s1, const char *s2, size_t n);
 extern char *strcpy(char *dest, const char *src);
 extern char *strncpy(char *dest, const char *src, size_t n);
+extern size_t strnlen(const char *s, size_t maxlen);
 extern size_t strlen(const char *s);
 extern char *strchr(const char *s, int c);
 extern char *strrchr(const char *s, int c);
diff --git a/library/libc.gmk b/library/libc.gmk
index c0a5faa..cf553aa 100644
--- a/library/libc.gmk
+++ b/library/libc.gmk
@@ -310,6 +310,7 @@ C_LIB := \
 	string_strncat.o \
 	string_strncmp.o \
 	string_strncpy.o \
+	string_strnlen.o \
 	string_strpbrk.o \
 	string_strrchr.o \
 	string_strspn.o \
diff --git a/library/string_strnlen.c b/library/string_strnlen.c
new file mode 100644
index 0000000..634a3b2
--- /dev/null
+++ b/library/string_strnlen.c
@@ -0,0 +1,75 @@
+/*
+ * $Id: string_strlen.c,v 1.4 2006-01-08 12:04:27 obarthel Exp $
+ *
+ * :ts=4
+ *
+ * Portable ISO 'C' (1994) runtime library for the Amiga computer
+ * Copyright (c) 2002-2015 by Olaf Barthel <obarthel (at) gmx.net>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   - Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *
+ *   - Neither the name of Olaf Barthel nor the names of contributors
+ *     may be used to endorse or promote products derived from this
+ *     software without specific prior written permission.
+ *
+ * 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 OWNER 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.
+ */
+
+#ifndef _STDLIB_NULL_POINTER_CHECK_H
+#include "stdlib_null_pointer_check.h"
+#endif /* _STDLIB_NULL_POINTER_CHECK_H */
+
+/****************************************************************************/
+
+#ifndef _STRING_HEADERS_H
+#include "string_headers.h"
+#endif /* _STRING_HEADERS_H */
+
+/****************************************************************************/
+
+size_t
+strnlen(const char *s, size_t maxlen)
+{
+	const char * start = s;
+	size_t result = 0;
+
+	assert( s != NULL );
+
+	#if defined(CHECK_FOR_NULL_POINTERS)
+	{
+		if(s == NULL)
+		{
+			__set_errno(EFAULT);
+			goto out;
+		}
+	}
+	#endif /* CHECK_FOR_NULL_POINTERS */
+
+	while((maxlen != 0) && ((*s) != '\0'))
+	{
+		s++;
+		maxlen--;
+	}
+
+	result = (size_t)(s - start);
+
+ out:
+
+	return(result);
+}