Øyestad is a former municipality in the old Aust-Agder county in Norway. The municipality existed from 1838 until 1992 when it was merged into the present-day municipality of Arendal which is now located in Agder county. At the time of its dissolution, the municipality of Øyestad encompassed most of the coastline between the towns of Grimstad and Arendal, along with the forested areas along the Nidelva river heading inland. Back in 1838, however, the municipality was far larger in size. The administrative centre was the village of Bjorbekk near the Bjorbekk Church.
The parish of Øiestad was established as a municipality on 1 January 1838 (see formannskapsdistrikt law). In 1846, the southern district of Øiestad (population: 2,806) was split off to form the new municipality of Fjære. The municipality was again split in 1850 when the northern district of Øiestad (population: 1,976) was separated to become the municipality of Froland. After that, Øiestad had 5,215 inhabitants. On 1 January 1875, an area of the neighboring town of Arendal (population: 52) was transferred to Øyestad. Then on 1 January 1881, the island of Hisøya and its small, surrounding islands (population: 2,652) were separated to form the new municipality of Hisøy. This left Øiestad with a population of 4,474. In the early 1900s, the spelling of the name was changed to Øyestad. In 1936, an area of Øyestad (population: 33) was transferred to neighboring Austre Moland municipality.
During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee. On 1 January 1962, the uninhabited area of Salvestjønn was transferred from Øyestad to the neighboring municipality of Landvik. On 1 January 1992, there was another large municipal merger. Øyestad (population: 8,679) was merged with the municipalities of Hisøy (population: 4,026), Tromøy (population: 4,711), Moland (population: 8,148), and the town of Arendal (population: 12,478) to form a new, much larger municipality of Arendal.