Askøy is a municipality in Hordaland county, Norway. The island municipality is located in the Midhordland district of the county, sitting in a large group of islands immediately northwest of the city of Bergen. The administrative centre of the municipality is the urban village of Kleppestø on the southeastern shore of the island of Askøy. Since the opening of the Askøy Bridge connecting it to the mainland of Bergen in 1992, the population has increased rapidly. Its population growth among the highest in Norway. In 2014, the 10-year population growth rate was 27%. Most of the population growth is due to immigration from Bergen and the surrounding districts of Nordhordland and Midhordland. It is also the most populous island in Norway.

The parish of Askøen was established as a municipality on 1 January 1838 (see formannskapsdistrikt). In 1879, a small area of the neighboring municipality of Fana (population: 18) was transferred to Askøen. On 1 January 1904, a small area near the village of Hanevik (population: 32) was transferred from Askøen to the neighboring municipality of Alversund. On 1 July 1918, the southern (mainland) portions of Askøy (population: 6,957) were separated from the municipality to form the new municipality of Laksevåg. This split left Askøy with 4,822 residents.

In 1963, the Schei Committee planned many municipal border adjustments, including some that involved Askøy. On 1 January 1964, the Hanevik area (population: 193) on the island of Askøy was transferred to Askøy from the municipality of Meland. Also on that date the old municipality of Herdla was dissolved. The parts of Herdla on the island of Askøy and the island of Herdla (population: 1,564) were also transferred to Askøy. This boundary adjustment put the entire island of Askøy, the island of Herdla, and many tiny surrounding islands in the municipality of Askøy.

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