Ishi (c. 1861 – March 25, 1916) was the last known member of the Native American Yahi people from the present-day state of California in the United States. The rest of the Yahi (as well as many members of their parent tribe, the Yana) were killed in the California genocide in the 19th century. Ishi, who was widely acclaimed as the "last wild Indian" in the United States, lived most of his life isolated from modern North American culture. In 1911, aged 50, he emerged at a barn and corral, 2 mi (3.2 km) from downtown Oroville, California.

Ishi, which means "man" in the Yana language, is an adopted name. The anthropologist Alfred Kroeber gave him this name because in the Yahi culture, tradition demanded that he not speak his own name until formally introduced by another Yahi. When asked his name, he said: "I have none, because there were no people to name me," meaning that there was no other Yahi to speak his name on his behalf.

Ishi was taken in by anthropologists at the University of California, Berkeley, who both studied him and hired him as a janitor. He lived most of his remaining five years in a university building in San Francisco. His life was depicted and discussed in multiple films and books, notably the biographical account Ishi in Two Worlds published by Theodora Kroeber in 1961.