| Abbr. | Logo | Ideology | Founded | Founder | Leader | Website | European Parliament Group |
| SDP |  | Social democracy | 20.07.1899 | Antti Lindtman | http://sdp.fi |  |
Elections
| Date | Elections | % | Votes | Seats | |
| 2023 | 19,93 | 616.218 | 43 | 3rd | |
| 2019 | EU | 14,62 | 267.342 | 2 | 2nd |
| 2019 | 17,73 | 546.471 | 40 | 1st | |
| 2015 | 16,51 | 490.102 | 34 | 4th | |
| 2014 | EU | 12,31 | 212.211 | 2 | 4th |
| 2011 | 19,10 | 561.558 | 42 | 2nd | |
| 2009 | EU | 17,54 | 292.051 | 2 | 3rd |
| 2007 | 21,44 | 594.194 | 45 | 3rd | |
| 2004 | EU | 21,16 | 350.525 | 3 | 3rd |
| 2003 | 24,47 | 683.223 | 53 | 2nd |
| Leaders | |
| 1899 – 1900 | Nils Robert af Ursin |
| 1900 | J. A. Salminen |
| 1900 – 1903 | K. F. Hellstén |
| 1903 – 1905 | Taavi Tainio |
| 1905 – 1906 | Emil Perttilä |
| 1906 – 1909 | Edvard Valpas-Hänninen |
| 1909 – 1911 | Matti Paasivuori |
| 1911 – 1913 | Otto Wille Kuusinen |
| 1913 – 1917 | Matti Paasivuori |
| 1917 – 1918 | Kullervo Manner |
| 1918 – 1926 | Väinö Tanner |
| 1926 – 1930 | Matti Paasivuori |
| 1930 – 1942 | Kaarlo Harvala |
| 1942 – 1944 | Väinö Salovaara |
| 1944 – 1946 | Onni Hiltunen |
| 1946 – 1957 | Emil Skog |
| 1957 – 1963 | Väinö Tanner |
| 1963 – 1975 | Rafael Paasio |
| 1975 – 1987 | Kalevi Sorsa |
| 1987 – 1991 | Pertti Paasio |
| 1991 – 1993 | Ulf Sundqvist |
| 1993 – 2005 | Paavo Lipponen |
| 2005 – 2008 | Eero Heinäluoma |
| 2008 – 2014 | Jutta Urpilainen |
| 2014 – 2020 | Antti Rinne |
| 2020 – 2023 | Sanna Marin |
| 2023 — | Antti Lindtman |
