William was first mentioned in a 949 deed as a count (
Graf) in
Thuringia. Originating from the
Saalfeld region, he held large estates around Weimar,
Jena, and
Apolda, possibly stemming from late Duke
Burchard of Thuringia, whose sons were expelled by King
Henry the Fowler in 913. He was probably married to Adela, a daughter of the
Popponid (
Elder House of Babenberg) duke
Poppo of Thuringia, margrave of the
Sorbian March, who had been deposed by the
East Frankish king
Arnulf in 892. William too appeared in the rank of a Thuringian
margrave. From 953 to 955, he and several
Wettin counts joined the revolt of Duke
Liudolf of Swabia against King
Otto the Great, wherefore he was temporarily deposed and exiled to the court of Otto's brother Duke
Henry of Bavaria. By 956, however, William was re-installed into his offices. He had at least three children: •
William II (d. 1003), called the Great, succeeded his father as Count of Weimar, Duke of Thuringia from 1002 • Poppo • Sigbert == Notes ==