Oemar Said Tjokroaminoto

(Raden Mas Hadji) Oemar Said Tjokroaminoto (August 16, 1882; Ponorogo – December 17, 1934; Yogyakarta), better known in Indonesia as H. O. S. Tjokroaminoto, was an Indonesian nationalist. He was one of the leaders, after the founder Haji Samanhudi, of Syarekat Dagang Islam (Islamic Trade Union), which became Sarekat Islam.