He rose to the position of mayor of Mongomo under the Spanish colonial government, and later served as a member of the territorial parliament. He became president in 1968 with the blessing of the Spanish government. During his presidency, his country was nicknamed "Auschwitz of Africa."
Macías Nguema's violations of human rights during his reign caused over one-third of Equatorial Guinea's population to flee to neighboring countries. The country's instruments of repression (military, presidential bodyguard) were entirely controlled by Macías Nguema's relatives and clan members. The president's paranoid actions included banning use of the world "intellectual" and crushing the country's infrastructure to prevent unlawful activities. He "Africanized" his name to Masie Nguema Biyogo Ñegue Ndong in 1976 after demanding that the same be done of the rest of the Equatoguinean population.
Toward the end of his rule, he declared himself President for Life. This turned out to have serious consequences, though, when nephew Teodoro Obiang Nguema Mbasogo overthrew and executed Macías Nguema in 1979.