Yamagata Prefecture (山形県, Yamagata-ken^?) is a prefecture of Japan located in the Tōhoku region on Honshu island. Its capital is Yamagata.

The aboriginal Ezo (蝦夷^?) people once inhabited the area now known as Yamagata. Yamagata and Akita Prefecture were known as Dewa Province until the Meiji Restoration.

During the Heian Period (794–1185), the Fujiwara (藤原^?) family ruled the area. Yamagata City flourished during the Edo Period (1603–1867) due to its status as a castle town and post station, famous for beni (red safflower dye used in the production of handspun silk). In 1689, the famous haiku poet, Matsuo Bashō visited Yamagata during his five-month trip to the northern regions of Japan.

Yamagata Prefecture is located in the southwest corner of Tōhoku, facing the Sea of Japan. It borders Niigata Prefecture and Fukushima Prefecture on the south, Miyagi Prefecture on the east, and Akita Prefecture on the north. All of these boundaries are marked by mountains, with most of the population residing in a limited central plain.