The Old Social Democratic Party of Germany (German: Alte Sozialdemokratische Partei Deutschlands), known as the Old Social Democratic Party of Saxony (German: Alte Sozialdemokratische Partei Sachsens) until 1927, was a political party in Germany. The party was a splinter group of the Social Democratic Party of Germany (SPD) in Saxony, and had nationalistic tendencies. Whilst the party failed to become a mass party, it played a significant role in regional politics in Saxony during the latter half of the 1920s. A leader of the party, Max Heldt, served as Minister-President of Saxony 1926-1929.Wilhelm Buck was the chairman of the party.
Between 1924 and 1926 Saxony had been ruled by a coalition of SPD and two liberal parties. The coalition government became unpopular amongst the SPD ranks, and the grassroots of the party revolted against the government participation. The leftist sector of the Saxony SPD preferred a 'Red' coalition of the SPD and the Communist Party of Germany. The SPD conference in Saxony in 1924 had called for the cooperation with the regional government to be terminated, but a significant number of deputies in the Landtag disobeyed the decision. From November 1924, expulsions of the dissident deputies started. In response, the expelled Landtag regional deputies formed a party of their own, the 'Old Social Democratic Party'. The Old Social Democratic Party issued a press release in April 1926, stating the programmatic goals of the party. The party was formally constituted on June 6, 1926. The dispute between the leftwing of SPD and the rightist parliamentarian wing (which formed the 'Old Social Democratic Party') in Saxony was labelled the Sachsenkonflikt.
In the summer of 1926 all members of the Old Social Democratic Party were purged from the SPD mass organizations, such as the Socialist Workers Youth.
The party started a newspaper of their own, Der Volkstaat.
The 'Old Social Democratic Party' expressed a shift in ideological discourse, downplaying class struggle for bourgeois ideas of citizenship. Soon after the foundation of the party, it began redefining itself, from viewing itself as the moderate wing of the German Social Democracy to a 'proletarian nationalist' ideological position (in contrast to the 'internationalist' and 'anti-state' SPD). The Volkstaat editor Ernst Niekisch (later a prominent National Bolshevik), whose influence within the party grew, was the architect of this process.