Stora Bornö is an island in Gullmarsfjorden, belonging to the Lysekil Municipality. Stora Bornö is about four kilometers long from north to south and is largely covered with pine forests. The island's highest point is 110 meters above sea level and in many places there are vertical slopes down towards the sea. The Bornö Marine Research Station was built on the island in 1902 by Otto Pettersson and Gustaf Ekman and is an oceanographic research facility still in operation.