Radøy is a former municipality in the Nordhordland district of the old Hordaland county, Norway. The municipality existed from 1964 until its dissolution in 2020 when it was merged into the new municipality of Alver in Vestland county. The municipality included almost all of the island of Radøy plus many small surrounding islands. The administrative centre of the municipality was the village of Manger. Other villages in the municipality included Askeland, Austmarka, Bøvågen, Haugland, Sæbø, and Sletta.
Prior to its dissolution in 2020, the municipality is the 372nd largest by area out of the 422 municipalities in Norway. Radøy is the 199th most populous municipality in Norway with a population of 5,128. The municipality's population density is and its population has increased by 10.1% over the last decade.
During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee. Radøy was created as a new municipality on 1 January 1964. The new municipality was constructed from parts of several different municipalities:
all of the municipality of Manger (population: 1,344)
all of the municipality of Hordabø (population: 1,679)
the island of Bognøy from Herdla municipality (population: 29)
most of the municipality of Sæbø, except the Titland area on the Lindås peninsula (population: 916)
the Sletta area on the island of Radøy from Lindås municipality (population: 305)
the Straume area on the island of Radøy and the small island of Fesøy from Austrheim municipality (population: 56)
On 1 January 2020, the neighboring municipalities of Meland, Radøy, and Lindås were merged into a large, new municipality called Alver.
The municipality is named after the island of Radøy (Rǫð) since the municipality encompassed the island. The first element is rǫð which means "row", "ridge", or "line" (here in the sense that it is a "long island" sticking out of the ocean). The last element, øy which means "island", was added later as a suffix to the name.