diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index e72d332b83..9985477efe 100644
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -274,6 +274,13 @@ print a message to stderr and exit with nonzero status.
 	Show the path to the shared index file in split index mode, or
 	empty if not in split-index mode.
 
+--show-object-format[=(storage|input|output)]::
+	Show the object format (hash algorithm) used for the repository
+	for storage inside the `.git` directory, input, or output. For
+	input, multiple algorithms may be printed, space-separated.
+	If not specified, the default is "storage".
+
+
 Other Options
 ~~~~~~~~~~~~~
 
diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index f8bbe6d47e..6c5d5d6a70 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -918,6 +918,17 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				show_datestring("--min-age=", arg);
 				continue;
 			}
+			if (opt_with_value(arg, "--show-object-format", &arg)) {
+				const char *val = arg ? arg : "storage";
+
+				if (strcmp(val, "storage") &&
+				    strcmp(val, "input") &&
+				    strcmp(val, "output"))
+					die("unknown mode for --show-object-format: %s",
+					    arg);
+				puts(the_hash_algo->name);
+				continue;
+			}
 			if (show_flag(arg) && verify)
 				die_no_single_rev(quiet);
 			continue;
diff --git a/t/t1500-rev-parse.sh b/t/t1500-rev-parse.sh
index 01abee533d..0177fd815c 100755
--- a/t/t1500-rev-parse.sh
+++ b/t/t1500-rev-parse.sh
@@ -59,6 +59,7 @@ test_rev_parse () {
 ROOT=$(pwd)
 
 test_expect_success 'setup' '
+	test_oid_init &&
 	mkdir -p sub/dir work &&
 	cp -R .git repo.git
 '
@@ -131,6 +132,20 @@ test_expect_success 'rev-parse --is-shallow-repository in non-shallow repo' '
 	test_cmp expect actual
 '
 
+test_expect_success 'rev-parse --show-object-format in repo' '
+	echo "$(test_oid algo)" >expect &&
+	git rev-parse --show-object-format >actual &&
+	test_cmp expect actual &&
+	git rev-parse --show-object-format=storage >actual &&
+	test_cmp expect actual &&
+	git rev-parse --show-object-format=input >actual &&
+	test_cmp expect actual &&
+	git rev-parse --show-object-format=output >actual &&
+	test_cmp expect actual &&
+	test_must_fail git rev-parse --show-object-format=squeamish-ossifrage 2>err &&
+	grep "unknown mode for --show-object-format: squeamish-ossifrage" err
+'
+
 test_expect_success 'showing the superproject correctly' '
 	git rev-parse --show-superproject-working-tree >out &&
 	test_must_be_empty out &&