Mengistu Haile Mariam (Amharic: መንግሥቱ ኀይለ ማርያም, pronunciation: [mənɡɨstu haɪlə marjam]; born 21 May 1937) is an Ethiopian former politician, revolutionary, and military officer who served as the head of state of Ethiopia from 1977 to 1991. He was General Secretary of the Workers' Party of Ethiopia from 1984 to 1991, chairman of the Derg—the Marxist–Leninist military junta that ruled Ethiopia—from 1977 to 1987, and president of the People's Democratic Republic of Ethiopia (PDRE) from 1987 to 1991.
The Derg seized power in the Ethiopian Revolution following the overthrow of Emperor Haile Selassie in 1974, marking the end of the Solomonic dynasty which had ruled Ethiopia since the 13th century. Mengistu purged his rivals within the Derg and made himself dictator of Ethiopia, attempting to modernize the feudal economy of Ethiopia through Marxist–Leninist-inspired policies such as nationalization and land redistribution. His bloody consolidation of power in 1977–1978 is known as the Ethiopian Red Terror—a brutal crackdown on opposition groups and civilians following a failed assassination attempt by the Ethiopian People's Revolutionary Party (EPRP) in September 1976, after it had ignored the Derg's invitation to join the union of socialist parties. The death toll is unknown but is estimated at between 30,000 and 750,000 by the Ethiopian Red Terror Documentation and Research Center.