Castillo Ross, Tudor-style castle in Viña del Mar, Chile.

Castillo Ross is a 1921 residence at the foot of Cerro Castillo in Viña del Mar, designed by architect Alberto Cruz Montt for businessman and politician Gustavo Ross Santa María. It stands on land that belonged to Ramón Nieto, owner of the hill's northwestern slope. The building has served as a private home and, since 1967, as the seat of the Club Unión Árabe.

Built in 1921 under architect Alberto Cruz Montt, the castle originally served as the home of businessman Gustavo Ross Santa María. Decades later, it transitioned to community use and has remained in that role ever since.

Since 1967 the building has been the headquarters of the Club Unión Árabe, a Chilean Arab community organization. The club's premises include a garden walkway named for the Lebanese-American poet Gibran Khalil Gibran, a detail visitors can look for in the grounds.

Public access to the castle is limited, but opens on a specific day each year for visitors to explore. Check in advance when this day occurs, as it follows a fixed schedule in May.

The building was commissioned in 1921 by Gustavo Ross Santa María and designed by architect Alberto Cruz Montt on land that had belonged to Ramón Nieto, owner of the northwestern slope of Cerro Castillo. In 1922 it passed to textile industrialist Luis Guevara, whose family kept it until 1967, when the Club Unión Árabe bought it for its headquarters. Viña del Mar's municipality declared it a Building of Historical and/or Architectural Interest on 9 May 2000.