The Ons Island (Galician: Illa de Ons; Spanish: Isla de Ons) is the main island of a small archipelago in the coast of Pontevedra in Galicia, Spain. Ons belongs administratively to the Galician municipality of Bueu, which has a regular ferry boat connection to the island, as have the mainland towns of Portonovo, Sanxenxo, Marín and Aldán.
In 2001 the European Union designated Ons a Special Protection Area for bird-life.
In 2002, along with several other archipelagos off the Pontevedra coast, Ons became part of the Atlantic Islands of Galicia National Park.