Centered on the arid Horn, east of the Ethiopian Highlands, the Horn of Africa Biodiversity Hotspot also covers the Rift Valley, which divides the Ethiopian Highlands into two major blocks, the xeric bushlands of northeastern Kenya and the southern coastal parts of the Arabian Peninsula. Politically, this includes most of Somalia, all of Djibouti, parts of Ethiopia, Eritrea, Kenya, Yemen and Oman, and a small piece of far north eastern Sudan. Also included in the hotspot are the Socotra Archipelago off the coast of northeastern Somalia, and a few hundred tiny islands in the Red Sea.

One of only two hotspots that is entirely arid, the region is home to a number of endemic and threatened antelope—the Vulnerable dibatag (Ammodorcas clarkei) and Endangered Speke’s gazelle (Gazella spekei) among them.

Other distinctive endemics found here include the Critically Endangered Somali wild ass (Equus africanus somaliensis) and the hamadryas baboon (Papio hamadryas). The Horn of Africa also holds more endemic reptiles than any other region on the continent.