diff --git a/include/stdlib.h b/include/stdlib.h
index 305aea4b867..82a347f5317 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -173,6 +173,8 @@ _Noreturn void
  */
 #if __ISO_C_VISIBLE >= 2023
 size_t	memalignment(const void *) __pure2;
+void	free_sized(void *, size_t) __noexcept;
+void	free_aligned_sized(void *, size_t, size_t) __noexcept;
 #endif /* __ISO_C_VISIBLE >= 2023 */
 
 /*
diff --git a/lib/libc/stdlib/malloc/Makefile.inc b/lib/libc/stdlib/malloc/Makefile.inc
index 3bae4ff1505..e7e3b49a355 100644
--- a/lib/libc/stdlib/malloc/Makefile.inc
+++ b/lib/libc/stdlib/malloc/Makefile.inc
@@ -1,3 +1,12 @@
 SYM_MAPS+=${LIBC_SRCTOP}/stdlib/malloc/Symbol.map
 
+.PATH: ${LIBC_SRCTOP}/stdlib/malloc
+
+MISRCS+=	free_aligned_sized.c \
+		free_sized.c
+
+MAN+=		free_sized.3
+
+MLINKS+=	free_sized.3 free_aligned_sized.3
+
 .include "${LIBC_SRCTOP}/stdlib/malloc/${OPT_LIBC_MALLOC}/Makefile.inc"
diff --git a/lib/libc/stdlib/malloc/Symbol.map b/lib/libc/stdlib/malloc/Symbol.map
index d3aa7f3f998..d1fefd8ca0c 100644
--- a/lib/libc/stdlib/malloc/Symbol.map
+++ b/lib/libc/stdlib/malloc/Symbol.map
@@ -47,6 +47,13 @@ FBSD_1.4 {
 	__mallctlbymib;
 };
 
+FBSD_1.9 {
+	free_sized;
+	free_aligned_sized;
+	__free_sized;
+	__free_aligned_sized;
+};
+
 FBSDprivate_1.0 {
 	_malloc_thread_cleanup;
 	_malloc_prefork;
diff --git a/lib/libc/stdlib/malloc/free_aligned_sized.c b/lib/libc/stdlib/malloc/free_aligned_sized.c
new file mode 100644
index 00000000000..6bb238e0b2b
--- /dev/null
+++ b/lib/libc/stdlib/malloc/free_aligned_sized.c
@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2026 Faraz Vahedi <kfv@kfv.io>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <sys/cdefs.h>
+#include <stdlib.h>
+
+void	__free(void *);
+
+void
+__free_aligned_sized(void *ptr, size_t alignment, size_t size)
+{
+
+	(void)alignment;
+	(void)size;
+	__free(ptr);
+}
+
+__weak_reference(__free_aligned_sized, free_aligned_sized);
diff --git a/lib/libc/stdlib/malloc/free_sized.3 b/lib/libc/stdlib/malloc/free_sized.3
new file mode 100644
index 00000000000..f208c829d93
--- /dev/null
+++ b/lib/libc/stdlib/malloc/free_sized.3
@@ -0,0 +1,100 @@
+.\"
+.\" Copyright (c) 2026 Faraz Vahedi <kfv@kfv.io>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd May 17, 2026
+.Dt FREE_SIZED 3
+.Os
+.Sh NAME
+.Nm free_sized ,
+.Nm free_aligned_sized
+.Nd C23 sized deallocation functions
+.Sh SYNOPSIS
+.Lb libc
+.In stdlib.h
+.Ft void
+.Fn free_sized "void *ptr" "size_t size"
+.Ft void
+.Fn free_aligned_sized "void *ptr" "size_t alignment" "size_t size"
+.Sh DESCRIPTION
+The
+.Fn free_sized
+function deallocates the memory referenced by
+.Fa ptr
+that was previously allocated by
+.Xr malloc 3 ,
+.Xr realloc 3 ,
+or
+.Xr calloc 3 .
+The
+.Fa size
+argument shall equal the size passed to the allocation function.
+The result of an
+.Xr aligned_alloc 3
+may not be passed to
+.Fn free_sized .
+.Pp
+The
+.Fn free_aligned_sized
+function deallocates memory referenced by
+.Fa ptr
+that was previously allocated by
+.Xr aligned_alloc 3 .
+The
+.Fa alignment
+and
+.Fa size
+arguments shall equal the values supplied to the allocation function.
+The result of an
+.Xr malloc 3 ,
+.Xr calloc 3 ,
+or
+.Xr realloc 3
+may not be passed to
+.Fn free_aligned_sized .
+.Pp
+If
+.Fa ptr
+is neither a null pointer nor a pointer returned by the allocation functions
+described above for the corresponding deallocation function, the behaviour is
+undefined, and so is supplying a
+.Fa size
+or
+.Fa alignment
+that does not match the original allocation.
+.Sh IMPLEMENTATION NOTES
+The C standard permits an implementation to ignore the
+.Fa size
+and
+.Fa alignment
+hints.
+The current implementation forwards to
+.Xr free 3
+without validating these arguments, so behaviour remains correct for
+well-formed use.
+.Pp
+These functions will be wired to the system allocator's sized deallocation,
+once supported, as with the rest of the memory allocation API, so that
+.Fa size
+and
+.Fa alignment
+hints are used for performance and security benefits.
+That behaviour conforms to the practice recommended for each function in the
+C standard.
+.Sh SEE ALSO
+.Xr free 3 ,
+.Xr malloc 3 ,
+.Xr calloc 3 ,
+.Xr realloc 3 ,
+.Xr aligned_alloc 3 ,
+.Xr jemalloc 3
+.Sh STANDARDS
+The
+.Fn free_sized
+and
+.Fn free_aligned_sized
+functions conform to
+.St -isoC-2023 .
+.Sh AUTHOR
+.An Faraz Vahedi Aq Mt kfv@kfv.io
diff --git a/lib/libc/stdlib/malloc/free_sized.c b/lib/libc/stdlib/malloc/free_sized.c
new file mode 100644
index 00000000000..b9242ac1386
--- /dev/null
+++ b/lib/libc/stdlib/malloc/free_sized.c
@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2026 Faraz Vahedi <kfv@kfv.io>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <sys/cdefs.h>
+#include <stdlib.h>
+
+void	__free(void *);
+
+void
+__free_sized(void *ptr, size_t size)
+{
+
+	(void)size;
+	__free(ptr);
+}
+
+__weak_reference(__free_sized, free_sized);
diff --git a/lib/libc/stdlib/memory.3 b/lib/libc/stdlib/memory.3
index b7703cf44bd..16674e8f208 100644
--- a/lib/libc/stdlib/memory.3
+++ b/lib/libc/stdlib/memory.3
@@ -25,7 +25,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd October 18, 2023
+.Dd May 17, 2026
 .Dt MEMORY 3
 .Os
 .Sh NAME
@@ -33,6 +33,8 @@
 .Nm alloca ,
 .Nm calloc ,
 .Nm free ,
+.Nm free_sized ,
+.Nm free_aligned_sized ,
 .Nm malloc ,
 .Nm posix_memalign ,
 .Nm realloc ,
@@ -53,6 +55,10 @@
 .Fn calloc "size_t nelem" "size_t elsize"
 .Ft void
 .Fn free "void *ptr"
+.Ft void
+.Fn free_sized "void *ptr" "size_t size"
+.Ft void
+.Fn free_aligned_sized "void *ptr" "size_t alignment" "size_t size"
 .Ft void *
 .Fn malloc "size_t size"
 .Ft int
@@ -79,6 +85,8 @@ individual manual pages.
 .Xr alloca 3 ,
 .Xr calloc 3 ,
 .Xr free 3 ,
+.Xr free_aligned_sized 3 ,
+.Xr free_sized 3 ,
 .Xr malloc 3 ,
 .Xr posix_memalign 3 ,
 .Xr realloc 3 ,
@@ -101,3 +109,10 @@ and
 .Fn posix_memalign
 functions conform to
 .St -p1003.1-2001 .
+.Pp
+The
+.Fn free_sized
+and
+.Fn free_aligned_sized
+functions conform to
+.St -isoC-2023 .