diff --git a/include/lib/libc/string_private.h b/include/lib/libc/string_private.h
new file mode 100644
index 0000000..da85fae
--- /dev/null
+++ b/include/lib/libc/string_private.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2025, Arm Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef STRING_PRIVATE_H
+#define STRING_PRIVATE_H
+
+/* Do not include outside of the libc. Use string.h instead. */
+
+#include <stddef.h>
+
+int memcmp(const void *s1, const void *s2, size_t len);
+int strcmp(const char *s1, const char *s2);
+int strncmp(const char *s1, const char *s2, size_t n);
+void *memchr(const void *src, int c, size_t len);
+char *strchr(const char *s, int c);
+void *memset(void *dst, int val, size_t count);
+size_t strlen(const char *s);
+char *strrchr(const char *p, int ch);
+
+#endif /* STRING_PRIVATE_H */