As of 2017, Paul Biya of Cameroon had been in power longer than any other African leader. He had been president for 35 years and prime minister for 7 years. The second longest serving president was Teodoro Obiang Nguema of Equatorial Guinea at 38 years. In third place was Robert Mugabe, who had been in power of Zimbabwe for 37 years. (https://wapo.st/2ID5jFp)