diff --git a/Documentation/git-merge-tree.txt b/Documentation/git-merge-tree.txt
index ffc4fbf7e8..9d37609ef1 100644
--- a/Documentation/git-merge-tree.txt
+++ b/Documentation/git-merge-tree.txt
@@ -69,6 +69,10 @@ OPTIONS
 	specify a merge-base for the merge, and specifying multiple bases is
 	currently not supported. This option is incompatible with `--stdin`.
 
+--write-pack::
+	Write any new objects into a separate packfile instead of as
+	individual loose objects.
+
 [[OUTPUT]]
 OUTPUT
 ------
diff --git a/builtin/merge-tree.c b/builtin/merge-tree.c
index 0de42aecf4..672ebd4c54 100644
--- a/builtin/merge-tree.c
+++ b/builtin/merge-tree.c
@@ -18,6 +18,7 @@
 #include "quote.h"
 #include "tree.h"
 #include "config.h"
+#include "bulk-checkin.h"
 
 static int line_termination = '\n';
 
@@ -414,6 +415,7 @@ struct merge_tree_options {
 	int show_messages;
 	int name_only;
 	int use_stdin;
+	int write_pack;
 };
 
 static int real_merge(struct merge_tree_options *o,
@@ -440,6 +442,7 @@ static int real_merge(struct merge_tree_options *o,
 	init_merge_options(&opt, the_repository);
 
 	opt.show_rename_progress = 0;
+	opt.write_pack = o->write_pack;
 
 	opt.branch1 = branch1;
 	opt.branch2 = branch2;
@@ -548,6 +551,8 @@ int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 			   &merge_base,
 			   N_("commit"),
 			   N_("specify a merge-base for the merge")),
+		OPT_BOOL(0, "write-pack", &o.write_pack,
+			 N_("write new objects to a pack instead of as loose")),
 		OPT_END()
 	};
 
diff --git a/merge-ort.c b/merge-ort.c
index 7857ce9fbd..e198d2bc2b 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -48,6 +48,7 @@
 #include "tree.h"
 #include "unpack-trees.h"
 #include "xdiff-interface.h"
+#include "bulk-checkin.h"
 
 /*
  * We have many arrays of size 3.  Whenever we have such an array, the
@@ -2107,10 +2108,19 @@ static int handle_content_merge(struct merge_options *opt,
 		if ((merge_status < 0) || !result_buf.ptr)
 			ret = error(_("failed to execute internal merge"));
 
-		if (!ret &&
-		    write_object_file(result_buf.ptr, result_buf.size,
-				      OBJ_BLOB, &result->oid))
-			ret = error(_("unable to add %s to database"), path);
+		if (!ret) {
+			ret = opt->write_pack
+				? index_blob_bulk_checkin_incore(&result->oid,
+								 result_buf.ptr,
+								 result_buf.size,
+								 path, 1)
+				: write_object_file(result_buf.ptr,
+						    result_buf.size,
+						    OBJ_BLOB, &result->oid);
+			if (ret)
+				ret = error(_("unable to add %s to database"),
+					    path);
+		}
 
 		free(result_buf.ptr);
 		if (ret)
@@ -3596,7 +3606,8 @@ static int tree_entry_order(const void *a_, const void *b_)
 				 b->string, strlen(b->string), bmi->result.mode);
 }
 
-static int write_tree(struct object_id *result_oid,
+static int write_tree(struct merge_options *opt,
+		      struct object_id *result_oid,
 		      struct string_list *versions,
 		      unsigned int offset,
 		      size_t hash_size)
@@ -3630,8 +3641,14 @@ static int write_tree(struct object_id *result_oid,
 	}
 
 	/* Write this object file out, and record in result_oid */
-	if (write_object_file(buf.buf, buf.len, OBJ_TREE, result_oid))
+	ret = opt->write_pack
+		? index_tree_bulk_checkin_incore(result_oid,
+						 buf.buf, buf.len, "", 1)
+		: write_object_file(buf.buf, buf.len, OBJ_TREE, result_oid);
+
+	if (ret)
 		ret = -1;
+
 	strbuf_release(&buf);
 	return ret;
 }
@@ -3796,8 +3813,8 @@ static int write_completed_directory(struct merge_options *opt,
 		 */
 		dir_info->is_null = 0;
 		dir_info->result.mode = S_IFDIR;
-		if (write_tree(&dir_info->result.oid, &info->versions, offset,
-			       opt->repo->hash_algo->rawsz) < 0)
+		if (write_tree(opt, &dir_info->result.oid, &info->versions,
+			       offset, opt->repo->hash_algo->rawsz) < 0)
 			ret = -1;
 	}
 
@@ -4331,9 +4348,13 @@ static int process_entries(struct merge_options *opt,
 		fflush(stdout);
 		BUG("dir_metadata accounting completely off; shouldn't happen");
 	}
-	if (write_tree(result_oid, &dir_metadata.versions, 0,
+	if (write_tree(opt, result_oid, &dir_metadata.versions, 0,
 		       opt->repo->hash_algo->rawsz) < 0)
 		ret = -1;
+
+	if (opt->write_pack)
+		end_odb_transaction();
+
 cleanup:
 	string_list_clear(&plist, 0);
 	string_list_clear(&dir_metadata.versions, 0);
@@ -4877,6 +4898,9 @@ static void merge_start(struct merge_options *opt, struct merge_result *result)
 	 */
 	strmap_init(&opt->priv->conflicts);
 
+	if (opt->write_pack)
+		begin_odb_transaction();
+
 	trace2_region_leave("merge", "allocate/init", opt->repo);
 }
 
diff --git a/merge-recursive.h b/merge-recursive.h
index b88000e3c2..156e160876 100644
--- a/merge-recursive.h
+++ b/merge-recursive.h
@@ -48,6 +48,7 @@ struct merge_options {
 	unsigned renormalize : 1;
 	unsigned record_conflict_msgs_as_headers : 1;
 	const char *msg_header_prefix;
+	unsigned write_pack : 1;
 
 	/* internal fields used by the implementation */
 	struct merge_options_internal *priv;
diff --git a/t/t4301-merge-tree-write-tree.sh b/t/t4301-merge-tree-write-tree.sh
index 250f721795..2d81ff4de5 100755
--- a/t/t4301-merge-tree-write-tree.sh
+++ b/t/t4301-merge-tree-write-tree.sh
@@ -922,4 +922,97 @@ test_expect_success 'check the input format when --stdin is passed' '
 	test_cmp expect actual
 '
 
+packdir=".git/objects/pack"
+
+test_expect_success 'merge-tree can pack its result with --write-pack' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+
+	# base has lines [3, 4, 5]
+	#   - side adds to the beginning, resulting in [1, 2, 3, 4, 5]
+	#   - other adds to the end, resulting in [3, 4, 5, 6, 7]
+	#
+	# merging the two should result in a new blob object containing
+	# [1, 2, 3, 4, 5, 6, 7], along with a new tree.
+	test_commit -C repo base file "$(test_seq 3 5)" &&
+	git -C repo branch -M main &&
+	git -C repo checkout -b side main &&
+	test_commit -C repo side file "$(test_seq 1 5)" &&
+	git -C repo checkout -b other main &&
+	test_commit -C repo other file "$(test_seq 3 7)" &&
+
+	find repo/$packdir -type f -name "pack-*.idx" >packs.before &&
+	tree="$(git -C repo merge-tree --write-pack \
+		refs/tags/side refs/tags/other)" &&
+	blob="$(git -C repo rev-parse $tree:file)" &&
+	find repo/$packdir -type f -name "pack-*.idx" >packs.after &&
+
+	test_must_be_empty packs.before &&
+	test_line_count = 1 packs.after &&
+
+	git show-index <$(cat packs.after) >objects &&
+	test_line_count = 2 objects &&
+	grep "^[1-9][0-9]* $tree" objects &&
+	grep "^[1-9][0-9]* $blob" objects
+'
+
+test_expect_success 'merge-tree can write multiple packs with --write-pack' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+
+		git config pack.packSizeLimit 512 &&
+
+		test_seq 512 >f &&
+
+		# "f" contains roughly ~2,000 bytes.
+		#
+		# Each side ("foo" and "bar") adds a small amount of data at the
+		# beginning and end of "base", respectively.
+		git add f &&
+		test_tick &&
+		git commit -m base &&
+		git branch -M main &&
+
+		git checkout -b foo main &&
+		{
+			echo foo && cat f
+		} >f.tmp &&
+		mv f.tmp f &&
+		git add f &&
+		test_tick &&
+		git commit -m foo &&
+
+		git checkout -b bar main &&
+		echo bar >>f &&
+		git add f &&
+		test_tick &&
+		git commit -m bar &&
+
+		find $packdir -type f -name "pack-*.idx" >packs.before &&
+		# Merging either side should result in a new object which is
+		# larger than 1M, thus the result should be split into two
+		# separate packs.
+		tree="$(git merge-tree --write-pack \
+			refs/heads/foo refs/heads/bar)" &&
+		blob="$(git rev-parse $tree:f)" &&
+		find $packdir -type f -name "pack-*.idx" >packs.after &&
+
+		test_must_be_empty packs.before &&
+		test_line_count = 2 packs.after &&
+		for idx in $(cat packs.after)
+		do
+			git show-index <$idx || return 1
+		done >objects &&
+
+		# The resulting set of packs should contain one copy of both
+		# objects, each in a separate pack.
+		test_line_count = 2 objects &&
+		grep "^[1-9][0-9]* $tree" objects &&
+		grep "^[1-9][0-9]* $blob" objects
+
+	)
+'
+
 test_done
