Diepold III, Margrave of Vohburg (c. 1079 – 1146), also known as Diepold von Vohburg and Diepold III von Giengen, was a Bavarian noble in the 12th century. His daughter, Adelheid of Vohburg, was the first wife of Frederick I, Holy Roman Emperor.
The title had originally referred to the families' holdings along the border with Bohemia, but after Diepold's death the title was transferred to the Bavarian lands proper of the family.
In 1133 Diepold III founded a Cistercian abbey at Waldsassen.