Sixt (or Sixtus) Birck, as Xystus Betuleius (February 24, 1501 – June 19, 1554) was a German humanist of Augsburg, "a notable German scholar of the New Learning".
At the end of his schooling in Augsburg the Protestant Reformation began. He continued his theological studies at Erfurt, Tübingen and Basel before returning to Augsburg as director (Magister) of the Gymnasium.