The college has educated prime ministers, world leaders, sportsmen and Booker Prize winners. Alumni of S. Thomas' College are referred to as "Old Thomians," and include D. S. Senanayake, the Head Mudaliyar of Ceylon, Sir Solomon Dias Bandaranaike, and three other Prime ministers. Many of the prominent leaders of the independence movement in the early twentieth century were educated at the College. These include Leslie Goonewardene, who founded Sri Lanka's first political party, the Lanka Sama Samaja Party and N. M. Perera, who served as leader of the opposition and the first Trotskyist to become a cabinet minister.