diff --git a/src/mongo/db/namespace_string.h b/src/mongo/db/namespace_string.h
index 22576d62b000d..2bce722ba46c5 100644
--- a/src/mongo/db/namespace_string.h
+++ b/src/mongo/db/namespace_string.h
@@ -900,15 +900,6 @@ inline StringData nsToDatabaseSubstring(StringData ns) {
     return ns.substr(0, i);
 }
 
-/**
- * "database.a.b.c" -> "database"
- *
- * TODO SERVER-123310: make this return a StringData
- */
-inline std::string nsToDatabase(StringData ns) {
-    return std::string{nsToDatabaseSubstring(ns)};
-}
-
 /**
  * "database.a.b.c" -> "a.b.c"
  */
diff --git a/src/mongo/db/namespace_string_test.cpp b/src/mongo/db/namespace_string_test.cpp
index 03a71f72db004..d361128683679 100644
--- a/src/mongo/db/namespace_string_test.cpp
+++ b/src/mongo/db/namespace_string_test.cpp
@@ -230,10 +230,6 @@ TEST_F(NamespaceStringTest, DbForSharding) {
 TEST_F(NamespaceStringTest, nsToDatabase1) {
     ASSERT_EQUALS("foo", nsToDatabaseSubstring("foo.bar"));
     ASSERT_EQUALS("foo", nsToDatabaseSubstring("foo"));
-    ASSERT_EQUALS("foo", nsToDatabase("foo.bar"));
-    ASSERT_EQUALS("foo", nsToDatabase("foo"));
-    ASSERT_EQUALS("foo", nsToDatabase(std::string("foo.bar")));
-    ASSERT_EQUALS("foo", nsToDatabase(std::string("foo")));
 }
 
 TEST_F(NamespaceStringTest, NamespaceStringParse1) {