Yamagata Prefecture (山形県, Yamagata-ken) is a prefecture of Japan located in the Tōhoku region of Honshu. It has a population of 1,005,926 (1 February 2025) and an area of 9,325 km (3,600 sq mi). Its neighbours are Akita Prefecture to the north, Miyagi Prefecture to the east, Fukushima Prefecture to the south, and Niigata Prefecture to the southwest.
The capital and largest city is Yamagata, with other major cities being Tsuruoka, Sakata and Yonezawa. The prefecture is located on Japan's western Sea of Japan coast and its borders with neighboring prefectures are formed by various mountain ranges, with 17% of its total land area being designated as Natural Parks. Yamagata Prefecture formed the southern half of the historic Dewa Province with Akita Prefecture and is home to the Three Mountains of Dewa, which includes the Haguro Five-story Pagoda, a recognised National Treasure of Japan.
