The Erfurt Program (German: Erfurter Programm) was the party platform adopted by the Social Democratic Party of Germany (SPD) at its party congress in Erfurt in 1891. Drafted under the political leadership of August Bebel and Wilhelm Liebknecht, and with theorist Karl Kautsky as its principal author, the program officially committed the SPD to Marxism. It was the first and most prominent in a series of similar Marxist-inspired platforms adopted by socialist parties across Europe.

The program represented a stark break from its predecessor, the Gotha Program of 1875, by rejecting the Lassallean idea of achieving socialism through state aid. Instead, it declared the impending death of capitalism and the necessity of class struggle. The program was divided into two parts. The first, the "maximalist" section, outlined the unalterable principles of a socialist transformation based on Marxist theory. The second, "minimalist" section, detailed a series of practical legislative goals to be pursued within the existing framework of the German Empire.

This dual structure allowed the Erfurt Program to accommodate the competing ideological currents within the party. It provided a theoretical justification for long-term revolutionary goals while enabling a practical, reformist political strategy. This "Erfurt Synthesis" guided the SPD's policies through the final decade of the 19th century and the first two decades of the 20th. However, the internal contradictions between its revolutionary theory and its gradualist practice became increasingly apparent, particularly in the face of the rise of Revisionism on the right and a new revolutionary left after 1905. The synthesis ultimately broke down, culminating in the formal split of the party during World War I. The program was formally superseded by the Görlitz Program [de] of 1921.

The unification of the German socialist movement in 1875 was achieved under the Gotha Program, a platform that was more heavily influenced by the ideas of Ferdinand Lassalle than by those of Karl Marx. The Gotha Program called for the "abolition of the iron law of wages through the cooperative control of collective labor" and pledged the party to work for a "free state" through "every legal means", without articulating a clear class character for the state or mentioning revolution.

The German socialist movement only became truly receptive to Marxism after Otto von Bismarck enacted the Anti-Socialist Laws in 1878. The twelve years of repression under these laws, which lasted until 1890, compelled the Socialists to operate illegally and fostered a growing revolutionary sentiment within the party and its working-class base. At its 1880 congress-in-exile in Wyden, Switzerland, the party unanimously voted to remove the phrase "by all legal means" from its program, and three years later at its Copenhagen congress, it declared itself to be a revolutionary party. During this period, the party's electoral support continued its irresistible surge, growing from 312,000 votes in the 1881 elections to 1,427,000 in the 1890 elections. This advance, in the face of legal persecution and electoral disappointments, fostered a sense of the historic invincibility of socialism among the party's theorists.

The period of illegality from 1878 to 1890, known in party histories as the "heroic epoch", was formative for the Social Democratic movement. Clandestine activities, such as the smuggling of the party newspaper Der Sozialdemokrat across the border, and the constant threat of arrest and imprisonment, gave the party a heightened sense of revolutionary identity. The experience of persecution also pushed the party's ideology in a more radical, Marxist direction. The party's Reichstag delegation (Fraktion) became its de facto leadership, as it was the only body that could operate with any degree of legality. A committee to revise the Gotha Program was formed at the 1887 party congress in St. Gallen, consisting of August Bebel, Wilhelm Liebknecht, and Ignaz Auer.

The party that emerged in 1890 was ideologically transformed. Where it had once been uncertain in its economic theories, it now had a firm commitment to Marxism. However, its commitment to its earlier democratic ideals had weakened. The experience of the Anti-Socialist Laws had estranged the socialists from the German liberal tradition, and the party developed an "ambivalent parliamentarism", participating in the parliamentary system while simultaneously rejecting its legitimacy. It needed a program that could reconcile the revolutionary fervour engendered by the years of persecution with the practical need for a reformist approach in a fundamentally non-revolutionary period. Marxist theory was seen as singularly appropriate for this task. The impetus for a new program was formally established at the party's 1890 congress in Halle, where Liebknecht reported that the press of time and events had prevented the drafting committee from fulfilling its charge. The congress voted unanimously for a new program to be presented at the next gathering.

To discredit the lingering Lassallean ideas, Friedrich Engels, a key intellectual leader for the German socialists, took the opportunity to publish Marx's Critique of the Gotha Programme, which had previously been withheld from the party membership. Karl Kautsky, the editor of the party's theoretical journal Die Neue Zeit, published the Critique in January 1891. This caused a "storm" within the party leadership, particularly upsetting Liebknecht and other members of the Reichstag delegation, but it successfully paved the way for the adoption of an explicitly Marxist program at the 1891 party congress in Erfurt.