It borders Cameroon on the north , Gabon on the south and east , and the Gulf of Guinea on the west . It used to be the Spanish colony of Spanish Guinea . Equatorial Guinea is bordered by Cameroon on the north , Gabon on the south and east , and the Gulf of Guinea on the west , where the island nation of SÃ # o TomÃ and PrÃ ncipe is located between Bioko and AnnobÃ n. Formerly the colony of Spanish Guinea , its post-independence name is suggestive of its location near both the equator and the Gulf of Guinea .