Yamanashi Prefecture is a landlocked administrative region situated in the Chūbu area of Honshu, Japan. It occupies a central position surrounded by Saitama, Nagano, Shizuoka, Kanagawa, and Tokyo. The landscape is dominated by the Kōfu Basin, which is encircled by the Akaishi Mountains and other high peaks. As one of only eight landlocked prefectures in the country, it serves as a vital geographic link between the capital region and the southern alpine zones.

The area was formerly known as Kai Province during the Heian period. It gained prominence under Takeda Shingen in the sixteenth century before being subsumed into the Tokugawa shogunate. The province was renamed Kōfu Prefecture in 1869 and officially became Yamanashi Prefecture in 1871. This transition is commemorated annually as Prefectural Citizen's Day on November twentieth, marking the establishment of its modern administrative identity.

Kōfu serves as the capital and largest city, anchoring the central basin alongside other major urban centers like Kai and Minamiarupusu. The prefecture hosts Mount Fuji, Japan's tallest mountain, which straddles the border with Shizuoka. Natural features include the Fuji Five Lakes region and extensive forested slopes. Twenty-seven percent of the land is designated as Natural Parks, including Chichibu Tama Kai and Minami Alps National Parks, preserving the rugged terrain.

The region attracts visitors through its cultural heritage, particularly the legacy of Takeda Shingen and sites like Maizuru Castle Park. Tourism is driven by outdoor excursions, wine tasting in Koshu, and fruit farming experiences. The prefecture offers a contrast to Tokyo's crowds with rural landscapes and historical towns. Travelers access these attractions via revitalized downtown areas and new residential facilities designed to boost local engagement.

The population stood at 803,963 as of 2021, though recent estimates place it near 787,592 in early 2025. The economy features strong industrial bases in robotics and jewelry, alongside significant agricultural output of grapes and peaches. Transport links include the Chūō Expressway and planned maglev lines. The climate is dry due to rain shadow effects, receiving approximately 818 mm of rainfall annually, making it suitable for viticulture.