diff --git a/man7/system_data_types.7 b/man7/system_data_types.7
index b8cbc8ffe..916efef08 100644
--- a/man7/system_data_types.7
+++ b/man7/system_data_types.7
@@ -629,6 +629,56 @@ C99 and later; POSIX.1-2001 and later.
 See also:
 .BR lldiv (3)
 .RE
+.\"------------------------------------- off_t ------------------------/
+.TP
+.I off_t
+.RS
+Include:
+.IR <sys/types.h> .
+Alternatively,
+.IR <aio.h> ,
+.IR <fcntl.h> ,
+.IR <stdio.h> ,
+.IR <sys/mman.h> ,
+.IR <sys/stat.h.h> ,
+or
+.IR <unistd.h> .
+.PP
+Used for file sizes.
+According to POSIX,
+this shall be a signed integer type.
+.PP
+Versions:
+.I <aio.h>
+and
+.I <stdio.h>
+define
+.I off_t
+since POSIX.1-2008.
+.PP
+Conforming to:
+POSIX.1-2001 and later.
+.PP
+See also:
+.BR fallocate (2),
+.BR lseek (2),
+.BR mmap (2),
+.BR mmap2 (2),
+.BR posix_fadvise (2),
+.BR pread (2),
+.BR preadv (2),
+.BR truncate (2),
+.BR fseeko (3),
+.BR getdirentries (3),
+.BR lockf (3),
+.BR posix_fallocate (3)
+.\".PP		TODO: loff_t, off64_t
+.\"See also the
+.\".I loff_t
+.\"and
+.\".I off64_t
+.\"types in this page.
+.RE
 .\"------------------------------------- pid_t ------------------------/
 .TP
 .I pid_t