Dagur Bergþóruson Eggertsson (born 19 June 1972) is an Icelandic politician who was the Mayor of Reykjavík from 2007 to 2008 and again from 2014 to 2024.

Dagur is formally educated as a physician[1] but also has a master's degree in Human Rights and International Law from the University of Lund in Sweden.

From 1995 to 1998, Dagur worked at the Icelandic National Broadcasting Service, Channel 1, making programs.

Dagur was first elected to Reykjavík City Council in May 2002 as an Independent candidate within the four party coalition Reykjavíkurlistinn.

Dagur became Mayor of Reykjavík in October 2007 but was suddenly ousted when one of his supporters in the Reykjavík City Council, Ólafur F. Magnússon, changed sides and formed a new majority with the opposition party, becoming mayor himself.