Johann Oldendorp (c. 1486[1] – 3 June 1567) was a German jurist and reformer.
He was the son of a merchant and the nephew (on his mother's side) of the historian Albert Krantz, from whom he probably received his early education.
In 1526 he moved to Rostock where he became a civic official: in 1534 he transferred to Lübeck and held a similar position.
In 1543, he went to Cologne and was recalled by Landgrave Philipp I of Hesse in July 1543 to Marburg.
Oldendorp wrote on topics that covered a variety of legal and philosophical issues regarding history; one of his printers was Andreas Kolbe.