Riek Machar Teny (born 1953) is a central figure in South Sudanese history, serving as the First Vice President. He leads the SPLM-IO (In Opposition), the main rival faction to President Salva Kiir. A clever but controversial politician, he has been involved in multiple rebellions and peace deals. In September 2025, his political standing faced a severe blow when he was suspended from the Vice Presidency and charged with treason following an attack on a military base, threatening the fragile peace agreement. His career has been defined by the ethnic conflict between the Nuer and Dinka, and his struggle for power in the world's youngest nation.