Bioko (spelled also Bioco, in Europe traditionally called Fernando Pó) is an island 32 km off the west coast of Africa, specifically Cameroon, in the Gulf of Guinea. It is the northernmost part of Equatorial Guinea with a population of 260,000 and an area of 2,017 km² (779 sq mi). It is volcanic with its highest peak the Pico Basile at 3,012 m (9,882 ft).

Bioko has a total area of 2,017 km² (779 sq mi). It is 70 km long from NNE to SSW and about 32 km across. It is volcanic and very mountainous with the highest peak Pico Basile (3,012 m (9,882 ft)). It thus resembles neighbouring islands São Tomé and Príncipe. Like them it lies on the Cameroon Line.

Bioko used to be the end of a peninsula attached to the mainland in what is now Cameroon, but it was cut off when sea levels rose 10,000 years ago at the end of the last ice age.

The island has a population of 260,000 inhabitants (2001), most of whom belong to the Bubi people. The rest of the population are Fernandinos, Spaniards and immigrants from Río Muni, Nigeria and Cameroon.