The Social Democratic Youth (Finnish: Sosialidemokraattiset Nuoret, also known as Demarinuoret) is the youth organisation of the Social Democratic Party of Finland.

[2] The organisation was founded in 1959 as a breakoff faction from the Social Democratic Youth League of Finland (SSN, founded 1921), which aligned with the SDP’s opposition, the Social Democratic Union of Workers and Smallholders.

[2] The Social Democratic Youth is a member of Young European Socialists (YES), the International Union of Socialist Youth (IUSY) and the Nordic Committee of Co-operating Social Democratic Youth (FNSU).

The Social Democratic Youth has 14 district organisations and one Swedish section, Finlands svenska unga socialdemokrater (FSUD).

Nationwide members of the league include the youth organisations of Finnish Metalworkers' Union and Trade Union for the Public and Welfare Sectors.