Gåsö, island in the Swedish province Bohuslän, county of Lysekil. Gåsö is situated at the entrance of the fiord Gullmarn and is a part of the Gullmarn nature reserve. The Gåsö archipelago consists partly of two larger islands, Gåsö and Storön, and partly of a large number of smaller islands. The old fishing village on the main island is today only inhabited during summer, when the population reaches approx 250 people.