diff --git a/lib/libc/aarch64/string/Makefile.inc b/lib/libc/aarch64/string/Makefile.inc
--- a/lib/libc/aarch64/string/Makefile.inc
+++ b/lib/libc/aarch64/string/Makefile.inc
@@ -20,6 +20,10 @@
 	strnlen \
 	strrchr
 
+
+MDSRCS+= \
+	memccpy.S
+
 #
 # Add the above functions. Generate an asm file that includes the needed
 # Arm Optimized Routines file defining the function name to the libc name.
diff --git a/lib/libc/aarch64/string/memccpy.S b/lib/libc/aarch64/string/memccpy.S
new file mode 100644
--- /dev/null
+++ b/lib/libc/aarch64/string/memccpy.S
@@ -0,0 +1,271 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2024 Getz Mikalsen <getz@FreeBSD.org>
+*/
+
+#include <machine/asm.h>
+
+	.weak	memccpy
+	.set	memccpy, __memccpy
+	.text
+
+ENTRY(__memccpy)
+	subs	x3, x3, #1
+	b.lo	.L0
+
+	dup	v0.16b,	w2
+
+	mov	x9, x0			// stash copy of src pointer
+	bic	x10, x1, #0xf		// src aligned
+	and	x11, x1, #0xf		// src offset
+
+	ldr	q1, [x10]
+	cmeq	v1.16b, v1.16b, v0.16b	// bytewise compare against src char
+
+	mov	x8, #-1			// prepare a 0xfff..fff register
+	mov	x6, #0xf
+
+	lsl	x12, x11, #2
+	lsl	x8, x8, x12		// mask of bytes in the string
+
+	shrn	v1.8b, v1.8h, #4
+	fmov	x5, d1
+
+	sub	x12, x11, #32
+	adds	x12, x12, x3		// distance from alignment boundary - 32
+	b.cc	.Lrunt			// branch if buffer length is 32 or less
+
+	ands	x8, x8, x5
+	b.eq	0f
+
+	/* match in first chunk */
+	rbit	x8, x8
+	clz	x8, x8			// index of mismatch
+	lsr	x8, x8, #2
+
+	sub	x8, x8, x11		// ... from beginning of the string
+
+	add	x0, x0, x8
+	add	x4, x9, x8		// dst + cnt
+	add	x5, x1, x8		// src + cnt
+	add	x0, x0, #1
+
+	b	.L0816
+
+0:
+	ldr	q3,	[x10, #16]	// load second string chunk
+	ldr	q2,	[x1]		// load true head
+	cmeq	v1.16b, v3.16b, v0.16b	// char found in second chunk?
+
+	/* process second chunk */
+	shrn	v1.8b, v1.8h, #4
+	fmov	x5, d1
+
+	cbz	x5, 0f
+
+	/* match in second chunk */
+	rbit	x8, x5
+	clz	x8, x8			// index of mismatch
+	lsr	x8, x8, #2
+
+	sub	x11, x11, #16
+	sub	x8, x8, x11		// adjust for alignment offset
+	add	x0, x0, x8		// return value
+	add	x0, x0, #1
+
+	add	x4, x9, x8
+	add	x5, x1, x8
+	b	.L1732
+
+0:
+	/* string didn't end in second chunk and neither did buffer */
+	ldr	q1,	[x10, #32]	// load next string chunk
+	str	q2,	[x0]		// deposit head into buffer
+	sub	x0, x0, x11		// adjust x0
+	mov	x3, x12
+	str	q3,	[x0, #16]	// deposit second chunk
+
+	add	x10, x10, #32		// advance src
+	add	x0, x0, #32		// advance dst
+	subs	x3, x3, #16		// enough left for another round?
+	b.lo	1f
+
+	/* main loop unrolled twice */
+	.p2align 4
+0:
+	cmeq	v2.16b, v1.16b, v0.16b	// char found in second chunk?
+	shrn	v2.8b, v2.8h, #4
+	fmov	x5, d2
+
+	cbnz	x5, 3f
+
+	str	q1, [x0]
+	ldr	q1, [x10, #16]		// load next chunk
+
+	cmp	x3, #16			// more than a full chunk left?
+	b.lo	2f
+
+	add	x10, x10, #32		// advance pointers
+	add	x0, x0, #32
+
+	cmeq	v2.16b, v1.16b, v0.16b	// char found in second chunk?
+	shrn	v2.8b, v2.8h, #4
+	fmov	x5, d2
+	cbnz	x5, 4f			// process chunk if match
+
+	str	q1, [x0, #-16]
+	ldr	q1, [x10]		// load next chunk
+
+	subs	x3, x3, #32
+	b.hs	0b
+
+1:
+	sub	x10, x10, #16		// undo second advancement
+	add	x3, x3, #16
+	sub	x0, x0, #16
+
+	/* 1--16 bytes left in the buffer but string has not ended yet */
+2:
+	cmeq	v2.16b, v1.16b, v0.16b	// char found in second chunk?
+	shrn	v2.8b, v2.8h, #4
+	fmov	x4, d2
+
+	lsl	x5, x3, #2		// shift 0xf to the limits position
+	lsl	x5, x6, x5
+	orr	x8, x4, x5		// insert match in mask at limit
+
+	rbit	x8, x8			// simulate x86 tzcnt
+	clz	x7, x8			// index of mismatch
+	lsr	x8, x7, #2
+
+	lsl	x5, x6, x7		// simulate x86 bt with shifted 0xf
+
+	add	x8, x8, #1
+	add	x0, x0, x8
+
+	ldr	q1, [x10, x8]		// load tail
+	str	q1, [x0]		// store tail
+
+	add	x0, x0, #16
+
+	tst	x4, x5			// terminator encountered inside buffer?
+	csel	x0, x0, xzr, ne		// if yes, return pointer, else NUL
+	ret
+
+4:
+	sub	x10, x10, #16		// undo second advancement
+	sub	x0, x0, #16		// undo second advancement
+
+3:
+	rbit	x8, x5
+	clz	x8, x8			// index of mismatch
+	lsr	x3, x8, #2
+
+	add	x0, x0, x3		// restore dst pointer
+	add	x10, x10, x3
+	ldr	q1, [x10, #-15]
+	str	q1, [x0, #-15]
+	add	x0, x0, #1
+	ret
+
+.Lrunt:
+	add	x13, x11, x3
+
+	mov	x7, x5			// keep a copy of original match mask
+
+	lsl	x4, x12, #2		// shift 0xf to the limits position
+	lsl	x4, x6, x4
+
+	cmp	x13, #16		// dont induce match if limit >=16
+	csel	x4, x4, xzr, lo
+	orr	x5, x5, x4		// insert match in mask at limit
+
+	ands	x8, x8, x5		// if match always fall through
+	b.ne	0f
+
+	ldr	q4,	[x10, #16]	// load second string chunk
+	cmeq	v1.16b, v4.16b, v0.16b	// char found in second chunk?
+
+	/* process second chunk */
+	shrn	v1.8b, v1.8h, #4
+	fmov	x8, d1
+	mov	x7, x8
+
+	lsl	x4, x12, #2
+	lsl	x4, x6, x4
+	orr	x8, x8, x4		// induce match in upper bytes of mask
+
+	rbit	x8, x8
+	clz	x4, x8			// index of mismatch
+	lsr	x8, x4, #2
+	add	x8, x8, #16		// no match in first chunk
+	b	1f
+
+0:
+	rbit	x8, x8
+	clz	x4, x8			// index of mismatch
+	lsr	x8, x4, #2
+1:
+	add	x0, x0, x8		// return value if terminator not found
+	sub	x0, x0, x11
+	add	x0, x0, #1
+
+	/* check if we encountered a match or the limit first */
+	lsl	x5, x6, x4
+	ands	x7, x7, x5		// was the terminator present?
+	csel	x0, xzr, x0, eq		// return value based on what we matched
+
+	sub	x8, x8, x11
+	add	x4, x9, x8		// dst + cnt
+	add	x5, x1, x8		// src + cnt
+
+	/* copy 17-32 bytes */
+.L1732:
+	cmp	x8, #16
+	b.lo	.L0816
+	add	x5, x5, #1		// ldp offsets are powers of 2
+	add	x4, x4, #1
+	ldp	x16, x17, [x1]
+	ldp	x12, x13, [x5, #-16]
+	stp	x16, x17, [x9]
+	stp	x12, x13, [x4, #-16]
+	ret
+
+	/* Copy 8-16 bytes */
+.L0816:
+	tbz	x8, #3, .L0407
+	ldr	x16, [x1]
+	ldr	x17, [x5, #-7]
+	str	x16, [x9]
+	str	x17, [x4, #-7]
+	ret
+
+	/* Copy 4-7 bytes */
+	.p2align 4
+.L0407:
+	cmp	x8, #3
+	b.lo	.L0103
+	ldr	w16, [x1]
+	ldr	w18, [x5, #-3]
+	str	w16, [x9]
+	str	w18, [x4, #-3]
+	ret
+
+	/* Copy 1-3 bytes */
+	.p2align 4
+.L0103:
+	lsr	x14, x8, #1
+	ldrb	w16, [x1]
+	ldrb	w15, [x5]
+	ldrb	w18, [x1, x14]
+	strb	w16, [x9]
+	strb	w18, [x9, x14]
+	strb	w15, [x4]
+	ret
+
+.L0:
+	eor	x0, x0, x0
+	ret
+
+END(__memccpy)