São Tomé and Príncipe, officially the Democratic Republic of São Tomé and Príncipe, is a Portuguese-speaking island nation in the Gulf of Guinea, off the western equatorial coast of Africa. It consists of two islands: São Tomé and Príncipe, located about 140 kilometers (87 mi) apart and about 250 and 225 kilometers (155 and 140 mi), respectively, off the northwestern coast of Gabon. Both islands are part of an extinct volcanic mountain range. São Tomé, the sizable southern island, is situated just north of the equator. It was named in honor of Saint Thomas by Portuguese explorers who happened to arrive at the island on his feast day.