Oscar Castellino is a baritone from Goa. While working as a software programmer, soprano Patricia Rozario OBE scouted him for his singing talent, and he traveled to London to study music at the Royal College of Music.

He debuted with the Welsh National Opera in 2019, singing George Benton in Dead Man Walking. In 2023, he sang the title role in the Barber of Seville at the first Bradford Opera Festival. 

Oscar is the composer of the Mars Anthem, which Mars Society USA commissioned in 2017. His other interests include Latin dancing and practicing calisthenics.