Bosaso, historically known as Bender Cassim is a city in the northeastern Bari province (gobol) of Somalia. It is the seat of the Bosaso District. Located on the southern coast of the Gulf of Aden, the municipality serves as the region's commercial capital and is a major seaport within the autonomous Puntland state.

The Gulf of Aden is a deepwater gulf of the Indian Ocean between Yemen to the north, the Arabian Sea to the east, Djibouti to the west, and the Guardafui Channel, Socotra and Somalia to the south. In the northwest, it connects with the Red Sea through the Bab-el-Mandeb strait, and it connects with the Arabian Sea to the east. To the west, it narrows into the Gulf of Tadjoura in Djibouti. The Aden Ridge lies along the middle of the Gulf and is causing it to widen about 15mm per year.