USNS Mission San Diego (T-AO-121)
 SS Mission San Diego was a Type T2-SE-A2 tanker built for the United States Maritime Commission during World War II. After the war she was acquired by the United States Navy as USS Mission San Diego (AO-121). Later the tanker transferred to the Military Sea Transportation Service as USNS Mission San Diego (T-AO-121). She was a member of the Mission Buenaventura-class oiler and was named for the Mission San Diego de Alcalá.