Barnim III the Great (c. 1300 – 14 August 1368) was a Pomeranian duke from the House of Griffin.

He ruled Pomerania-Stettin in the years 1344–1368, although he had been a co-regent of his father Otto I since 1320, taking a prominent part in the defence and government of the duchy.

Aiming for independence from the Margraviate of Brandenburg, he allied himself with Poland and Bohemia.

The civil war in Brandenburg in the years 1349–1354 allowed Barnim III to extend his duchy by conquest.

Barnim III married Agnes (c. 1318 – before or in 1371), a daughter of Duke Henry II of Brunswick-Grubenhagen.