Ona, also known as Selk'nam (Shelknam), is a language spoken by the Selk'nam people in Isla Grande de Tierra del Fuego in southernmost South America.

The Selk'nam genocide was the systematic extermination of the Selk'nam people, one of the four indigenous peoples of Tierra del Fuego, in the late 19th and early 20th centuries. Historians estimate that the genocide spanned a period of between ten and twenty years, and resulted in the decline of the Selk'nam population from approximately 4,000 people during the 1880s to a few hundred by the early 1900s.