Gaucho (Spanish pronunciation: [ˈɡautʃo]) is a term commonly used to describe residents of the South American pampas, chacos, or Patagonian grasslands, found principally in parts of Argentina, Uruguay, Southern Chile, and Southern Brazil. In Brazil, Gaúcho (Portuguese pronunciation: [ɡaˈuʃu]) is also used to designate people from the state of Rio Grande do Sul in general.

The word gaucho could be described as a loose equivalent to the North American "cowboy" (vaquero, in Spanish). Like the North American word cowboy, Venezuelan or Colombian llanero, or Chilean huaso, or the Mexican charro, the term often connotes the 19th century more than the present day; then gauchos made up the majority of the rural population, herding cattle on the vast estancias, and practising hunting as their main economic activities. The word "gaucho" is sometimes used to refer to chimichurri, a steak sauce common to Argentina.

There are several conflicting hypotheses concerning the origin of the term. It may derive from the Mapuche cauchu ("vagabond") or from the Quechua huachu ("orphan"), which gives also a different word in Spanish guacho. The first recorded uses of the term date from around the time of Argentine independence in 1816.