diff --git a/usr.bin/grep/grep.1 b/usr.bin/grep/grep.1
index 1cc72ea239e1..1aa72155a57d 100644
--- a/usr.bin/grep/grep.1
+++ b/usr.bin/grep/grep.1
@@ -30,7 +30,7 @@
 .\"
 .\"	@(#)grep.1	8.3 (Berkeley) 4/18/94
 .\"
-.Dd April 25, 2018
+.Dd May 7, 2018
 .Dt GREP 1
 .Os
 .Sh NAME
@@ -404,6 +404,13 @@ and block buffered otherwise.
 .El
 .Pp
 If no file arguments are specified, the standard input is used.
+Additionally,
+.Dq -
+may be used in place of a file name, anywhere that a file name is accepted, to
+read from standard input.
+This includes both
+.Fl f
+and file arguments.
 .Sh EXIT STATUS
 The
 .Nm grep
diff --git a/usr.bin/grep/grep.c b/usr.bin/grep/grep.c
index 827c6b987a0f..3d22b3fb1259 100644
--- a/usr.bin/grep/grep.c
+++ b/usr.bin/grep/grep.c
@@ -307,7 +307,9 @@ read_patterns(const char *fn)
 	size_t len;
 	ssize_t rlen;
 
-	if ((f = fopen(fn, "r")) == NULL)
+	if (strcmp(fn, "-") == 0)
+		f = stdin;
+	else if ((f = fopen(fn, "r")) == NULL)
 		err(2, "%s", fn);
 	if ((fstat(fileno(f), &st) == -1) || (S_ISDIR(st.st_mode))) {
 		fclose(f);
@@ -324,7 +326,8 @@ read_patterns(const char *fn)
 	free(line);
 	if (ferror(f))
 		err(2, "%s", fn);
-	fclose(f);
+	if (strcmp(fn, "-") != 0)
+		fclose(f);
 }
 
 static inline const char *