The Socialist Workers' Party of Germany (, SAPD) was a centrist Marxist political party in Germany. It was formed by a left-wing party with around 20,000 members which split off from the SPD in the autumn of 1931. In 1931, the remnants of USPD merged into the party, and in 1932 some Communist Party dissenters joined the group too, as well as a part from the Communist Party Opposition. Nevertheless, its membership remained small. From 1933, the group's members worked illegally against National Socialism.