John III, Duke of Mecklenburg-Stargard (1389 – after 11 November 1438) was from 1416 to 1438 Duke of Mecklenburg, Lord of Stargard, Sternberg, Friedland, Fürstenberg, and Lychen.
He was the oldest child of Duke John II and his wife Catherine (Wilheida) of Lithuania.
He was released on 28 June 1427, under the condition that he had to swear an oath of allegiance to the Margrave of Brandenburg.
He married Luttrud, the daughter of Albert IV of Anhalt-Köthen.
John III died in 1438 and was probably buried in Sternberg.