The Municipality of Oia is an administrative region of Santorini and includes the northern part of Santorini and the island of Thirassia.

It took its present form in 1997 when the former communities of Oia and Thirasssia were abolished and a new community was established the "Municipality of Oia". This new community has two community districts, Oia and Thirassia. The headcourters of the "Municipality of Oia" are located at the village of Oia.

The community district of Oia is located in the northwestern part of Santorini and includes the settlements: Oia, Finikia, Tholo, Armeni, Amoudi, Mavri Petra (now Paradise) and Kouloumpo. The community district of Thirassia includes the settlements: Agia Irini (Riva), Manola, Potamo, Korfo, Agrilia and Kera. Most settlements are traditional settlements and are declared official traditional with presidential decrees.

The population was 1,230 inhabitants at the 2001 census, and the land area is 19.449 km². The population and land area are distributed as follows: 962 persons on 10.150 km² in Santorini, and 268 persons on 9.299 km² in Therasia. The average altitude is 121m.

Today the Municipality office has 30 permanent and 7 seasonal employees.