Parliamentary elections were held in Finland on 20 and 21 March 1966. The Social Democratic Party (SDP) overtook the Centre Party as the largest faction in Parliament. Rafael Paasio of the SDP subsequently became Prime Minister and formed a popular front government consisting of the SDP, the Centre Party, the People's Democratic League (SKDL), and the Social Democratic Union of Workers and Smallholders (TPSL) in May 1966.