No, it was not Mathieu Kerekou of Benin.

Because my adviser [I doubt he reads this blog] spent some of his early years in academia working and publishing on Somalia, I have been reminded quite a few times that back in 1967 Somalia’s president Aden Abdulle Osman Daar was actually the first leader of independent Africa to lose an election and agree to step down [see here].

This is a fact that many Africanists and journalists have forgotten. Please give credit where it is due.