The Social Democratic Party of Finland is a social democratic and pro-European political party in Finland. It is the third largest party in the Parliament of Finland with 43 seats. Founded in 1899 as the Workers' Party of Finland, 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, Socialist International and SAMAK.

Pro-Europeanism, sometimes called European Unionism, is a political position that favours European integration and membership of the European Union (EU).