Príncipe is the smaller, northern major island of the country of São Tomé and Príncipe lying off the west coast of Africa. It has an area of 136 square kilometres (53 sq mi) and a population of approximately 5,000. The island is a heavily eroded volcano speculated to be over three million years old, surrounded by smaller islands including Ilheu Bom Bom, Ilhéu Caroço, Tinhosa Grande and Tinhosa Pequena. Part of the Cameroon Line archipelago, Príncipe rises in the south to 948 metres at Pico de Príncipe, in a thickly forested area forming part of the Obo National Park.
The island was uninhabited when discovered by the Portuguese and named «Príncipe» (Prince's island) in honor of Afonso, Prince of Portugal, his father's favorite. Subsequently, the north and centre of the island were made into plantations, most of them formed by Portuguese colonialists using slave labor. These concentrated initially on producing sugar and later on cocoa, becoming the world's greatest cocoa producer. Since independence, these plantations have largely reverted to forest.
Príncipe was the site where Einstein's Theory of Relativity was experimentally proved successful by Arthur Stanley Eddington and his team during the total solar eclipse of May 29, 1919.