The 90-square-kilometre (35 sq mi) island is located entirely inside the municipality of Askøy.

Since the opening of the Askøy Bridge leading to the mainland in the city of Bergen in 1992, the population has increased rapidly.

[1] Askøy is surrounded by fjords: the Hjeltefjorden lies to the west and north, the Byfjorden to the east, and the Herdlefjorden to the northeast.

The areas around the bridge (where the villages of Kleppestø and Strusshamn are located) and along the east coast (around the village of Florvåg and Erdal) are densely populated due to their proximity to the city of Bergen across the fjord.

The large lake Askevatnet lies along the eastern shore of the island.