Motlanthe, Kgalema Petrus (kälāˈmä, mōtlänˈtā) [key], 1949–, South African politician, b. Johannesburg. A fierce opponent of apartheid, he was influenced by Steve Biko and organized student protests and joined the militant wing of the African National Congress (ANC). Motlanthe was jailed for almost a year in 1976 and the following year was convicted of terrorism and sentenced to 10 years imprisonment on Robben Island, where he served alongside Nelson Mandela and Jacob Zuma. Upon his release (1987), he joined the National Union of Mineworkers, became a skilled negotiator, and in 1992 was named leader of the powerful union. He was elected secretary-general of the ANC in 1997 and became its deputy president a decade later. When Thabo Mbeki stepped down as South Africa's president in 2008 while Zuma was embroiled in accusations of corruption, Motlanthe was named the nation's interim president. He served until May, 2009, when Zuma was elected president; Motlanthe then became South Africa's deputy president. Motlanthe challenged Zuma for the ANC chairmanship in 2012 but lost.