USS Michigan (SSGN-727) arrived in Busan, South Korea after a six-year absence, reflecting U.S. commitment to the Indo-Pacific region.
The port visit comes in the wake of North Korea firing two ballistic missiles into Japan's exclusive economic zone.
U.S. submarine forces have been conducting exercises, training, operations, and military cooperation activities with South Korean allies.
Previous port calls to Busan have been made by other U.S. ships, including USS Ronald Reagan (CVN-76) and USS Robert Smalls (CG-52).
The visit was included in the Washington Declaration signed by the presidents of the U.S. and South Korea in April.
USS Michigan is one of the Navy's converted Ohio-class submarines equipped with Tomahawk Land Attack Missiles.
The submarine carries 154 land-attack missiles with a range of over 1,000 nautical miles, capable of launching from under the sea.
The presence of the submarine serves as a warning and was publicly announced, following recent attacks on U.S. troops and merchant ships in the region.