Movimiento de Izquierda-Verde
Before becoming Prime Minister, she was chairperson of the Left-Green Movement. In the wake of the 2017 Icelandic parliamentary election, President Guðni Th. Jóhannesson tasked Katrín with forming a governing coalition to consist of the Left-Green Movement, the Progressive Party, the Social Democratic Alliance, and the Pirate Party. Coalition talks between the four parties formally began on 3 November 2017, but were unsuccessful because of Progressive Party concerns that her coalition would have too thin a majority. As a result, she sought to lead a three-party coalition with the Independence Party and Progressive Party. After coalition talks were completed, President Guðni formally granted Katrín a mandate to lead the government, which was installed on 30 November. She is the second woman to serve as Prime Minister of Iceland.