- For the Spanish-Californian rancher, see Guillermo Castro.
Guillermo Antonio Castro Orellana (born 25 June 1940 in San Salvador) is a retired footballer from El Salvador.
Nicknamed el Loro (the Parrot), he has most notably played for local side Atlético Marte, with whom he made his debut in 1960. He has also had spells at UES and Juventud Independiente.
Castro represented his country at the 1968 Summer Olympics, in five FIFA World Cup qualification matches and at the 1970 FIFA World Cup in Mexico.
He has been involved with El Salvador's coaches association for 30 years and has also managed league sides Independiente de San Vicente, Chalatenango and Atlético Marte.