Sandøy is an island municipality in Møre og Romsdal county, Norway. It is part of the Romsdal region. The administrative centre is the village of Steinshamn. Other villages include Ona and Myklebost. The municipality is spread out over many islands in the mouth of the Romsdalsfjord.
The municipality of Sandø i Romsdal was established on 1 January 1867 when it was separated from the municipality of Akerø. The initial population was 601. The spelling of the name was later changed to Sandøy. On 1 January 1965, the Myklebost area on Harøya and some smaller islands to the west (population: 287) were transferred from Haram to Sandøy.
The municipality (originally the parish) is named after the farm and the small island, Sandøya (Old Norse: Sandøy), since the first church was built there. The first element is sandr which means "sand" and the last element is øy which means "island". The name was historically spelled Sandø or Sandøen.