Reykjavík Constituency South (Icelandic: Reykjavíkurkjördæmi suður [ˈreiːcaˌviːkʏrˌcʰœrˌtaiːmɪ ˌsʏːðʏr̥]) is one of the six constituencies of Iceland. Its consists of southern parts of Reykjavík, the capital city of Iceland. It elects 11 members to the Althing.
The border between the two Reykjavík constituencies is decided by the National Electoral Commission before each parliamentary election with the goal of having the number of electors in each constituency as close as possible to equal.
Reykjavík South borders the Reykjavík North, South and Southwest constituencies. It is the smallest constituency in Iceland by area.
The constituency includes the southern part of the city of Reykjavík, part of the urban region of the Capital Region.