Raden Mas Hadji Oemar Said Tjokroaminoto (16 August 1882 – 17 December 1934),[1] better known in Indonesia as H.O.S. Tjokroaminoto, was an Indonesian nationalist. He became one of the leaders of the Islamic Trade Union (Indonesian: Syarekat Dagang Islam), founded by Samanhudi, which became Sarekat Islam, which they both co-founded.[2][3]
