North Africa or Northern Africa is the northernmost region of Africa. The United Nations definition of Northern Africa includes seven countries and territories; Algeria, Egypt, Libya, Morocco, Sudan, Tunisia, and Western Sahara. Algeria, Morocco, Tunisia, Libya, often Mauritania and Western Sahara form the Maghreb, while Egypt and Sudan comprise the Nile Valley (so named after the Nile River, which has two tributaries; the White Nile and Blue Nile). Egypt is a transcontinental country because of the Sinai Peninsula, which geographically lies in West Asia. North Africa also includes a number of Spanish possessions (Ceuta and Melilla and tiny Spanish islets off the coast of Morocco). The Canary Islands and the Portuguese Madeira Islands, in the North Atlantic Ocean northwest of the African mainland, are sometimes included in considerations of the region.