Castaño is a Spanish surname meaning "auburn".
- Carlos Castaño Gil (1965–2004), founder of the Peasant Self-Defense Forces of Córdoba and Urabá (ACCU), an extreme right paramilitary organization in Colombia
- Carlos Castaño Panadero (born 1979), Spanish cyclist
- Catalina Castaño (born 1979), Colombian tennis player
- Cecilia Castaño (born 1953), Spanish academic
- Cristina Castaño (born 1978), Spanish actress
- Daniel Fernández del Castaño (born 1979), Argentine model
- Diego Castaño (born 1979), Argentine footballer
- Dolly Montoya Castaño (born 1948), Colombian professor and scientist
- Eliodoro Castaño Pedrosa (1933–2019), Moroccan-born Spanish footballer
- Enrique Castaño (born 1993), Spanish footballer
- Ezequiel Castaño (born 1981), Argentine actor
- Fidel Castaño, right-wing Colombian drug lord and paramilitary leader
- Francisco Castaño (born 1972), Spanish footballer
- Francisco Sans Castaño (1868–1937), Spanish painter and engraver
- Gabriel Castaño (born 1997), Mexican swimmer
- Gaspar Castaño de Sosa (c. 1550–c. 1595), Portuguese colonial settler and converso
- Gastón Castaño (born 1985), Argentine footballer
- Gonzalo Fernández-Castaño (born 1980), Spanish golfer
- Héctor Castaño (born 1965), Colombian road cyclist
- Jorge Castaño (born 1981), Colombian wrestler
- Jose Castaño (1854–?), Spanish Franciscan friar
- Juan David Castaño Montoya (born 1990), Colombian singer better known by his stage name Llane
- Juanma Castaño (born 1977), Spanish sports commentator
- Miguel Castaño (1883–1936), Spanish politician
- Mónica Castaño (born 1989), Colombian model
- Pepe Castaño (born 1999), Spanish footballer
- Santiago Castaño (born 1995), American soccer player
- Sergio Castaño (born 1982), Spanish footballer
- Stefany Castaño (born 1994), Colombian footballer
- Tony Castaño (1911–1989), Cuban baseball player
- Vicente Castaño (born 1957), also known as El Profe, Colombian paramilitary leader
- Yolanda Castaño (born 1977), Galician painter