The Horn of Africa (HoA), also known as the Somali Peninsula, is a large peninsula and geopolitical region in East Africa. Located on the easternmost part of the African mainland, it is the fourth largest peninsula in the world. It is composed of Somalia, Djibouti, Ethiopia, and Eritrea. Although not common, broader definitions include parts or all of Kenya and Sudan. It has been described as a region of geopolitical and strategic importance, since it is situated along the southern boundary of the Red Sea; extending hundreds of kilometres into the Gulf of Aden, Guardafui Channel, and Indian Ocean, it also shares a maritime border with the Arabian Peninsula.