The two islands Fjelbergøy and Borgundøy as located at the southern edge of Sunnhordland, bordering Rogaland the south. The island is only accessible via sea, either using ferries or high-speed crafts, with daily routes from Halsnøy, Utbjoa and Stord. Today, the islands have around 30 full-time inhabitants, but more than 100 seasonal inhabitants who stay there for longer periodes during summer. Most of the settlements houses are located on Fjelbergøy. The island also has its own general store and festival hall.
The parish of Fjældberg was established as a formannskapsdistrikt on January 1, 1838. According to the 1835 census the municipality had a population of 2,986 at the time. Already in 1855 the municipality Eid was incorporated into Fjelberg, increasing its population to 4,794. In 1865 the parish Vikebygd, with 1,062 inhabitants, was merged with a part of Finnås municipality to create the new municipality Sveen. In 1898 a part of Stord with 117 inhabitants was moved to Fjelberg. On 1 July 1916 Ølen was split from Fjelberg to constitute a municipality of its own, leaving Fjelberg with 1,926 inhabitants. On January 1, 1965, as part of the nationwide merging of municipalities, Fjelberg was incorporated into Kvinnherad, along with parts of Skånevik. Prior to the merger Fjelberg had a population of 2,308.