Oia (Greek: Οία, pronounced [ˈi.a]) is a former community on the islands of Thira (Santorini) and Therasia, in the Cyclades, Greece. Since the 2011 local government reform it is part of the municipality Santorini, of which it is a municipal unit. It covers the whole island Therasia and the most north west part of Santorini, which it shares with the municipal unit of Santorini. 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.
Along the cliff of Oia, houses have been delved into the porous volcanic rock (left over from a large volcanic explosion many years ago that sunk the center of the island). Parts of these houses are visible and the scenery that results from it is generally perceived as being typically Greek. The town is noted for its picturesque architecture, unique for its blend of relatively large (for the town’s space) medieval Venetian houses (dubbed “kapetanospita” gr: “καπετανόσπιτα” – as they belonged to the captains) with small in cave village homes, called “yposkafa” (gr: “υπόσκαφα”, caved-in) which were the housing form of the rest of the town’s population. This is a reminiscent of the age of Venetian rule over the island. Other attributes of this era are the large Catholic population as well as the medieval fortifications to protect from pirates. To this day laws protect the natural and architectural beauty of the town from modern manifestations, such as public electrical wires