Thira (Greek: Περιφερειακή ενότητα Θήρας) is one of the regional units of Greece. It is part of the region of South Aegean. The regional unit covers the islands of Thira (Santorini), Anafi, Folegandros, Ios, Sikinos and several smaller islands in the Aegean Sea.
As a part of the 2011 Kallikratis government reform, the regional unit of Thira was created out of the former Cyclades Prefecture. It is subdivided into 5 municipalities. These are (number as in the map in the infobox):
The province of Thira (Greek: Επαρχία Θήρας) was one of the provinces of the Cyclades Prefecture. It had the same territory as the present regional unit. It was abolished in 2006.