SS Mission Santa Ynez 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 Santa Ynez (AO-134). Later the tanker transferred to the Military Sea Transportation Service as USNS Mission Santa Ynez (T-AO-134). A Mission Buenaventura-class oiler, she was named for Mission Santa Inés located in Solvang, California.

Mission Santa Inés was a Spanish mission in present-day Solvang, California, United States, and named after St. Agnes of Rome. Founded on September 17, 1804, by Father Estévan Tapís of the Franciscan order, the mission site was chosen as a midway point between Mission Santa Barbara and Mission La Purísima Concepción, and was designed to relieve overcrowding at those two missions and to serve the Indians living north of the Coast Range. Sunset magazine editors wrote of the Hidden Gem of the Missions: “With its simple, straightforward exterior, Santa Inés fits one’s impression of how a ripe old mission should look.”