Abstract <p>On the continental margin of Tanzania, two large sedimentary basins—the Tanzanian and Rovuma—are distinguished. Within the Tanzanian Basin, the following six subbasins are distinguished from north to south along the littoral: the Tanga, Pemba-Zanzibar, Latam, Rufidji, Mafia, and Mandawa. A large part of Tanzania is situated on the East African Plateau. The sedimentary cover of the basin is represented by Phanerozoic deposits 7–10 km thick on the Archean basement. The Rovuma Basin consists of two blocks, the Mrvara and Linde. The basin is characterized as a passive continental margin with a complex tectonic history. Rovuma basin is the principal gas-bearing basin in the country. The formation of gas accumulations on the southeastern continental margin of Africa is associated with the range of the Karoo Complex, dated to the Permian–Triassic. Analysis of more than 25 discoveries of gas fields on the Tanzanian continental margin results in the conclusion that all the discovered gas fields are confined mainly to the western side of the blocks. A large gas accumulation has been in deepwater areas, on the slope. Moreover, large gas discoveries have been made in southern Tanzania. Farther north, the quantity and reserves of gas fields decreases. In northern Tanzania, gas accumulations have not been found, but oil accumulations have been noted.</p>