Diego Gelmírez or Xelmírez (Latin Didacus Gelmirici) (ca 1069 – ca 1140) was the second bishop (from 1100) and first archbishop (from 1120) of the Catholic Archdiocese of Santiago de Compostela in Galicia, modern Spain. He is a prominent figure in the history of Galicia and an important historiographer of the Iberia of his day. Diego involved himself in many quarrels, ecclesiastical and secular, which were recounted in the Historia Compostelana, which covered his episcopacy from 1100 to 1139 and serves as a sort of of the bishop's life.