Hokkaido (Japanese: 北海道, Hepburn: Hokkaidō, pronounced [hokkaꜜidoː] (listen); lit. 'Northern Sea Circuit') is Japan's second largest island and comprises the largest and northernmost prefecture, making up its own region. The Tsugaru Strait separates Hokkaidō from Honshu; the two islands are connected by the undersea railway Seikan Tunnel.

The largest city on Hokkaidō is its capital, Sapporo, which is also its only ordinance-designated city. Sakhalin lies about 43 kilometers (26 mi) to the north of Hokkaidō, and to the east and northeast are the Kuril Islands, which are administered by Russia, though the four most southerly are claimed by Japan. Hokkaidō was formerly known as Ezo, Yezo, Yeso, or Yesso.

Although there were Japanese settlers who had ruled the southern tip of the island since the 16th century, Hokkaido was considered foreign territory that was inhabited by the indigenous people of the island, known as the Ainu people. While geographers such as Mogami Tokunai and Mamiya Rinzō explored the island in the Edo period, Japan's governance was limited to Oshima Peninsula until the 17th century. The Japanese settlers began their migration to Hokkaido in the 17th century, which often resulted in clashes and revolts between Japanese and Ainu populations. In 1869, following the Meiji Restoration, Ezo was annexed by Japan under on-going colonial practices, and renamed Hokkaido. After this event, Japanese settlers started to colonize the island. While Japanese settlers colonized the island, the Ainu people were dispossessed of their land, forced to assimilate, and aggressively discriminated against by the Japanese settlers.