The first element is derived from the word karmr which means "bargeboard", likely in the sense of a "sheltering island".

The official blazon is "Gules, a fret argent" (Norwegian: I rødt et sølv gitterkryss).

This means the arms have a red field (background) and the ordinary is a fret (a diamond interwoven with a cross).

The ordinary 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 design is canting, as the central diamond shape stands for karm (which is Norwegian for a "frame").

The cross in the design symbolizes the local Avaldsnes Church that was the royal chapel here during the Middle Ages.

The eddic poem Grímnismál says that Thor, the weather god, wades the Karmsundet strait every morning on his way to Yggdrasil, the tree of life.

The Karmsundet strait was also the source of the name of the kingdom, at the time when the first king of the unified Norway, Harald Fairhair, lived on Karmøy.

[12] In the 18th century, two girls from Uyea in Shetland rowed to Haaf Gruney to milk some of the cows grazing there.

Unfortunately, their return was marred by a strong storm, and eventually they found their tiny boat blown to Karmøy.

The natural and cultural landscape is highly heterogeneous, encompassing chalk-white sands, moorland, and several piers around the island.

The landscape in the north is mainly agricultural, while large parts of the inland south are heather moors.

The island has many white, sandy beaches facing the North Sea, attracting surfers as one of the top spots for windsurfing in Norway.

On the mainland part of Karmøy, the village of Norheim is contiguous with the neighboring town of Haugesund.

Other villages in Karmøy include Avaldsnes, Eike, Ferkingstad, Sævelandsvik, Sandve, Veavågen, and Visnes.