SÃ # o TomÃ and PrÃ ncipe is formed by two volcanic islands - the biggest of which is S. TomÃ - and several islets , and is located in the Gulf of Guinea , off the Western equatorial coast of Africa . SÃ # o TomÃ and PrÃ ncipe , officially the Democratic Republic of SÃ # o TomÃ and PrÃ ncipe , is a Portuguese-speaking island nation in the Gulf of Guinea , off the western equatorial coast of Central Africa .