Kvitsøy is an island municipality in Rogaland county, Norway. At only 6.29-square-kilometre (2.43 sq mi), it is the smallest municipality in Norway by area and one of the smallest by population. Kvitsøy is located in the traditional district of Ryfylke. The administrative centre of the municipality is the village of Ydstebøhamn on the island of Kvitsøy. The municipality is an archipelago located at the entrance to the large Boknafjorden. It sits about 2 nautical miles (3.7 km; 2.3 mi) northwest of the mainland Stavanger peninsula.

The Rogfast tunnel system is currently being built during the 2020s to connect Kvitsøy to the mainland road network via the European route E39 highway.

The 6-square-kilometre (2.3 sq mi) municipality is the 356th largest by area out of the 356 municipalities in Norway, making it the smallest in the nation. Kvitsøy is the 349th most populous municipality in Norway with a population of 535. The municipality's population density is 85.2 inhabitants per square kilometre (221/sq mi) and its population has increased by 1.3% over the previous 10-year period.

The islands of Kvitsøy were established as a municipality on 1 January 1923 when they were separated from the municipality of Mosterøy. Initially, the municipality had 581 residents. The municipal boundaries have not changed since that time.

The municipality (originally the parish) is named after the Kvitsøy islands (Old Norse: Hvítingsøyjar) since the islands make up the whole parish/municipality. The first element is derived from the word hvítr which means "white". The last element derives from the word eyjar which means "islands". Thus the name means "the white islands", probably because there is white quartz in the rocks on the islands. Originally, the spelling of the municipality was "Kvitingsø", but later it was shortened to "Kvitsøy".

The coat of arms was granted on 25 May 1989. The official blazon is "Azure, three lighthouses argent, two over one" (Norwegian: I blått tre sølv fyrlykter, 2-1). This means the arms have a blue field (background) and the charge is a set of three lighthouse tops. The charge has a tincture of argent which means it is commonly colored white, but if it is made out of metal, then silver is used. The choice of lighthouses and the color blue are symbolic of the importance of the sea for this island municipality. The arms were designed by Even Jarl Skognlund. The municipal flag has the same design as the coat of arms.

The Church of Norway has one parish (sokn) within the municipality of Kvitsøy. It is part of the Tungenes prosti (deanery) in the Diocese of Stavanger.

Kvitsøy is first mentioned in the Snorre Saga, where Snorre records a truce being made between King Olaf II of Norway later to be known as St. Olav (Norwegian: Hellige Olav) and Erling Skjalgsson, under the stone cross. Later it seems that the islands were owned by the Church until the reformation in 1536 (when the nation switched from Roman Catholicism to Lutheranism), when it became Crown property. In 1591, the population had become large enough to fund the construction of the Kvitsøy Church, which is still standing and the first new church in the county after the reformation. From the mid-18th century, Kvitsøy was the location of one of the first navigation beacons in western Norway, and this was later converted to a lighthouse service when the Kvitsøy Lighthouse was built. Kvitsøy Vessel Traffic Service Centre opened on 3 January 2003.