Yamagata Domain was a feudal domain in Edo period Japan, located in Dewa Province, Japan. It was centered on Yamagata Castle in what is now the city of Yamagata. Unlike some han whose control was relatively stable throughout the Edo period (1603–1867), Yamagata changed hands a great number of times during its history.

Dewa Province was a province of Japan comprising modern-day Yamagata Prefecture and Akita Prefecture, except for the city of Kazuno and the town of Kosaka. Dewa bordered on Mutsu and Echigō Provinces. Its abbreviated form name was Ushū (羽州).