Social Democratic Party of Finland

The Social Democratic Party of Finland (Finnish: Suomen sosialidemokraattinen puolue Finnish pronunciation: [ˈsuo̯men ˈsosiɑ(ː)liˌdemokrɑːtːinen ˈpuo̯lue], SDP, nicknamed: demarit in Finnish; Swedish: Finlands socialdemokratiska parti, SD) is a social democratic political party in Finland. It is the third-largest party in the Parliament of Finland with a total of 43 seats.

Founded in 1899 as the Workers' Party of Finland (Finnish: Suomen työväenpuolue; Swedish: Finlands arbetarparti), the SDP is Finland's oldest active political party and has a close relationship with the Central Organisation of Finnish Trade Unions. It is also a member of the Party of European Socialists, Progressive Alliance and Socialist International.

Following the resignation of Antti Rinne in December 2019, Sanna Marin became the country's 46th prime minister. The SDP formed a new coalition government on the basis of its predecessor, the Rinne Cabinet, in effect continuing its cooperation with the Centre Party, Green League, Left Alliance and Swedish People's Party. Of the nineteen ministerial spots that were decided upon in conjunction, seven of them were designated to the SDP in the Marin Cabinet. In September 2023, Antti Lindtman was elected as leader of the party following Marin's resignation after the 2023 Finnish parliamentary election.