Frederick III may refer to:

Frederick III "the restless" of Brunswick-Göttingen-Calenberg (born: 1424; died: 5 March 1495 in Hann. Münden ), was a son of Duke William the Victorious of Brunswick-Lüneburg and Cecilia of Brandenburg. He became Duke of Brunswick-Lüneburg together with his brother William IV in 1482. However, he was deposed in 1484.

Emperor Frederick III may refer to:

Frederick III James of Hesse-Homburg (born 19 May 1673 in Cölln; died: 8 June 1746 in 's-Hertogenbosch ) was a Landgrave of Hesse-Homburg