Welf I, Duke of Bavaria, duke of Bavaria.
Welf I (c. 1035/1040 – 6 November 1101) was Duke of Bavaria from 1070 to 1077 and from 1096 to his death. He was the first member of the Welf branch of the House of Este. In the genealogy of the Elder House of Welf he is counted as Welf IV.