The east African millipede genus Obelostreptus Attems, 1909 is revised to include four species, new distribution records are given, and a new combination is established. In addition, the genus is removed from the family Harpagophoridae and placed in the Spirostreptidae. A new species, O. bilamellatus VandenSpiegel sp. n. from Kenya is described, and Mardonius nakitawa (Silvestri 1907) is removed from the genus Mardonius Attems, 1914 to become the fourth known species, O. nakitawa comb. n., in Obelostreptus. An identification key to the species of Obelostreptus based on male gonopod structure is also presented.