diff --git a/lib/libc/amd64/string/Makefile.inc b/lib/libc/amd64/string/Makefile.inc
index 2baa631fb3fa..ee396f98eccc 100644
--- a/lib/libc/amd64/string/Makefile.inc
+++ b/lib/libc/amd64/string/Makefile.inc
@@ -1,22 +1,23 @@
 MDSRCS+= \
 	amd64_archlevel.c \
 	bcmp.S \
 	memchr.S \
 	memcmp.S \
 	memcpy.S \
 	memmove.S \
 	memset.S \
 	stpcpy.S \
 	strcat.S \
 	strchrnul.S \
 	strcmp.S \
 	strcpy.c \
 	strcspn.S \
 	strlen.S \
 	strncmp.S \
 	strnlen.c \
 	strpbrk.c \
 	strrchr.S \
+	strsep.c \
 	strspn.S \
 	timingsafe_bcmp.S \
 	timingsafe_memcmp.S
diff --git a/lib/libc/amd64/string/strsep.c b/lib/libc/amd64/string/strsep.c
new file mode 100644
index 000000000000..9fda56d7e135
--- /dev/null
+++ b/lib/libc/amd64/string/strsep.c
@@ -0,0 +1,57 @@
+/*-
+ * Copyright (c) 2023 The FreeBSD Foundation
+ *
+ * This software was developed by Robert Clausecker <fuz@FreeBSD.org>
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * 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 AUTHOR 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 AUTHOR 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
+ */
+
+#include <sys/cdefs.h>
+#include <string.h>
+
+size_t __strcspn(const char *, const char *);
+
+/*
+ * We have a fast strcspn() on amd64.  Use it over a direct
+ * implementation of strsep for better performance.
+ */
+char *
+strsep(char **stringp, const char *delim)
+{
+	size_t n;
+	char *s;
+
+	s = *stringp;
+	if (s == NULL)
+		return (NULL);
+
+	n = __strcspn(s, delim);
+	if (s[n] == '\0')
+		*stringp = NULL;
+	else {
+		s[n] = '\0';
+		*stringp = s + n + 1;
+	}
+
+	return (s);
+}