Dedi (or Dedo) (1004 – October 1075) was the Margrave of the Saxon Ostmark (also called Lower Lusatia) from 1046 and a claimant for the title of Margrave of Meissen from 1069. He was the second son of Dietrich II of Wettin and Matilda, daughter of Eckard I of Meissen.
Dedi inherited the Ostmark from its last dynast, the childless Odo II, because he had married his sister, Oda (died before 1068). Oda was herself the widow of William III of Weimar and mother of William and Otto, margraves of Meissen successively. When Otto his stepson died, Dedi married his widow, Adela of Louvain, and in her name claimed the Meissen March.
Otto died in 1067 and was succeeded by Egbert I, but Dedi married his widow in 1069 and rebelled. In claiming the Meissen March through his wife, Dedi was challenging the royal prerogative in the marches. With him in his revolt was Albert II of Ballenstedt, who raided the monastery of Nienburg, a foundation of the family of Dedi's first wife. Adela of Louvain for her part aggressively supported her husband, so much so that Lambert of Hersfeld was compelled to call her a saevissima uxor (rough meaning "raging wife"). Adalbert of Bremen, one of the regents of the young king Henry IV, frustrated the Thuringian rebels and preserved the peace in Thuringia and Meissen. Dedi was confined to Lusatia, where he was succeeded by his eldest son, Dedi II.
Dedi left a daughter, Adelaide, by his first wife Oda, who married Ernest, Margrave of Austria. By Adela of Louvain, Dedi had two sons: Henry, who later ruled both Lusatia and Meissen, and Conrad, who died in battle with the Wends.