Barbara Thornton (January 6, 1950 – November 8, 1998) was an American singer, musicologist, and groundbreaking performer of medieval music. Thornton, described as “one of the most eminent medieval voices of our time” (), was born in Summit, New Jersey and educated at Sarah Lawrence College, the Conservatorium van Amsterdam, and the Schola Cantorum Basiliensis. In 1977, she founded the ensemble Sequentia with Benjamin Bagby in Basel. They moved to Cologne that same year, where they lived and worked together for 21 years (; ; ).