Red Vienna (German: Rotes Wien) was the colloquial name for the capital of Austria between 1918 and 1934, during which the Social Democratic Workers' Party of Austria (SDAP) maintained near-total political control over Vienna (and for a short time, over Austria as a whole). During this time, the SDAP pursued a rigorous program of construction projects across the city in response to severe housing shortages. This involved implementing policies to improve public education, healthcare, and sanitation, while attempting to create the architectural foundation for a new socialist lifestyle.

The collapse of the First Austrian Republic in 1934 after the suspension of the Nationalrat by Bundeskanzler Engelbert Dollfuß a year earlier, and the subsequent banning of the SDAP in Austria, brought an end to the period of the first socialist project in Vienna. Many of the housing complexes built during this period, known in German as Gemeindebauten, still survive today.

After the defeat of the Austro-Hungarian Empire in World War I, the Treaty of Saint-Germain-en-Laye was signed between the Empire and the victorious Entente, which stipulated the complete disassembly of the component lands of the Empire into individual nations. Austrian control was reduced to the rump Republic of German-Austria, officially proclaimed on 12 November 1918. During the war, the German current within the Social Democrats expressed an interest in the idea of Mitteleuropa proposed by the pan-Germanic nationalist movement within Austria, hoping that a union (Anschluß) with the rest of Germany could stymie some of the major economic problems the new republic was beginning to face.

To the disheartenment of the Social Democrats and pan-Germanic nationalists alike, the Treaty of Saint-Germain-en-Laye expressly forbade any future union with the newly founded Weimar Republic, leaving Austria with little territory and limited access to the Hungarian breadbasket that had fed Vienna for decades. In the 4 May 1919 Gemeinderat (en: Municipal Council) elections in the capital, the SDAP gained a majority of seats, with the office of the Mayor of Vienna won by SDAP politician Jakob Reumann. Nationally, the success of the SDAP was far less pronounced; it won only 43.4% of the seats (40.8% of the popular vote) necessitating a coalition government with the conservative Christian Social Party (CSP), an uncomfortable accommodation from which the SDAP would never fully recover. During the Gemeinderat elections of 4 May 1919, for the first time in Austrian history, all adult citizens of both sexes had voting rights. The Social Democrats elected prominent Austromarxist and SDAP member Karl Renner as the interim Staatskanzler, but after the national elections in 1920 concluded with the CSP candidate Michael Mayr succeeding Renner in his position, the SDAP did not manage to elect another national-level leader for the remainder of the First Republic's existence.

Vienna underwent a host of demographic changes that exacerbated the economic issues in the city in the years during and immediately after the war. Refugees from Austrian Galicia, including roughly 25,000 Jews seeking to avoid the political and antisemitic violence of the Russian Civil War that had spread to the area, had settled in the capital city. At the end of the war, many former soldiers of the Imperial and Royal Army came to stay in Vienna, while many former Imperial-Royal government ministry officials returned to their native lands, creating a large exchange of various ethnic populations in and out of Vienna in the years that followed.

The middle classes, many of whom had bought war bonds that were now worthless, were plunged into poverty by hyperinflation. New borders between Austria and the nearby regions rendered food supply difficult by cutting off the city from lands that had traditionally fed it for centuries. Existing apartments were overcrowded, and diseases such as tuberculosis, the Spanish flu, and syphilis raged. In the new Austria, Vienna was considered a capital much too big for the small country, and often called Wasserkopf (en: "big head") by people living in other parts of the country.

On the other hand, optimists saw the dire postwar situation as an opportunity for great sociopolitical transformation. Pragmatic intellectuals like Hans Kelsen, who drafted the republican constitution, and Karl Bühler applied themselves to this work. For them it was a time of awakening, of new frontiers and of optimism.

The intellectual resources of Red Vienna were remarkable. Socialist intellectuals like Ilona Duczyńska and Karl Polanyi relocated to Vienna, joining the city's native Sigmund Freud, Alfred Adler, Karl Bühler, Arthur Schnitzler, Karl Kraus, Ludwig Wittgenstein, Adolf Loos, Arnold Schoenberg and Vienna's many other scientists, artists, publishers and architects. Intellectuals of conservative persuasions, such as radical Catholic nationalists Joseph Eberle [de], Hans Eibl [de], and Johannes Messner [de], also lived within the SDAP-run capital over the course of the First Republic's existence.