The Ainu are a group of people in northern Japan whose traditional life was based on a hunting, fishing, and plant-gathering economy; the word ainu means "man." Only about 18,000 Ainu now live on Hokkaidō, the northernmost island of Japan, but the population was much larger in the past and their homeland included at least southern Sakhalin, the Kurile Islands, northern parts of Honshū (the main island of Japan), and adjacent areas.
Not only was their hunting-gathering economy vastly different from that of the neighboring Japanese, Koreans, and Chinese, who had been agriculturalists for several millennia, but they spoke a language of their own, and certain physical characteristics distinguished them from their neighbors.
Far from being monolithic, Ainu culture has been rich in intracultural variation. This article introduces only some of the major differences and similarities among the three major Ainu groups: the Kurile, Sakhalin, and Hokkaidō Ainu. The Hokkaidō Ainu and the Sakhalin Ainu reside on the island of Hokkaidō and the southern half of the island of Sakhalin, respectively. Some use the term "Kurile Ainu" to refer only to the Ainu who occupied the central and northern Kurile Islands, excluding the Ainu on the southern Kuriles, whose way of life was similar to that of the Hokkaidō Ainu. Others use the label "Kurile Ainu" to refer to the Ainu on all the Kurile Islands, which is the practice followed in this article. The island of Sakhalin south of 50° N had always been the homeland of the Sakhalin Ainu, while the territory north of 50° N belonged to the Gilyaks and other peoples.