The Seventh World Congress of the Communist International (Comintern) was a multinational conference held in Moscow from 25 July through 20 August 1935 by delegated representatives of ruling and non-ruling communist parties from around the world and invited guests representing other political and organized labor organizations. The gathering was attended by 513 delegates, of whom 371 were accorded full voting rights, representing 65 Comintern member parties as well as 19 sympathizing parties.

The gathering is best remembered for its endorsement of a Popular Front of communist and non-communist forces against the growing menace of fascism in Europe, paving the way for advocacy of collective security between the Soviet Union and the various capitalist states of Europe. This marked a dramatic reversal of the Comintern's previous orientation towards class warfare endorsed by the 6th World Congress of 1928, the aggressive line of the so-called "Third Period."

Throughout the early 1930s the Soviet Union's People's Commissariat of Foreign Affairs, headed by Maxim Litvinov, had pursued a policy of attempting to win a broad international agreement to bring about military disarmament. This initiative had clearly reached a terminal impasse from the Nazi seizure of power in January 1933, however, with the new political reality writ large by the October 1933 departure of Nazi Germany from the Geneva disarmament negotiations.

Still, there was little motion among the world communist movement towards construction of a broader united front with the socialist movement and their affiliated trade unions, with the Comintern continuing to train its rhetorical guns on the social democratic movement, which was held to have sabotaged the effort of the Communist Party of Germany to wage battle against fascism by propagating what the communists characterized as its "anti-Marxist theory of a 'peaceful,' 'democratic' road to socialism" among the German workers' movement.

There were some within the communist movement who began feeling their way to a new more collaborative orientation, however. The February 1934 Uprising of Socialists against right wing forces in Austria and movement towards cooperation between Socialists and Communists in France in fighting a nascent fascist movement there convinced Bulgarian Communist Georgi Dimitrov, a leading figure in the Communist International that the Comintern's hostility towards joint action between Communists and Socialists was ill-considered. Dimitrov made his triumphant return to Moscow in April 1934 following acquittal in the Reichstag Fire trial determined to change the Comintern's fundamental strategy from one of antagonistic opposition to social democracy to one of cooperation in a joint struggle.

Preparations for a 7th World Congress of the Comintern began in Moscow late in 1934, with the Executive Committee of the Communist International (ECCI) establishing a commission to draft programmatic resolutions for that body. This body was divided between Dimitrov and others advocating a move towards a "general democratic, anti-Fascist" orientation and hardliners who continued to argue that the battle against fascism was inseparable from the task of overthrowing the bourgeoisie, implying a simultaneous fight against the fascist right and the reformist constitutionalist and socialist movements. With no rapid agreement forthcoming, on 8 March 1935, the scheduled opening of the 7th Congress was moved back to the end of July.

It would be the exigencies of Soviet foreign policy which ultimately shaped the Comintern's orientation, when on 2 May 1935, the two countries most concerned about the implications of growing German militarism — France and the Soviet Union — concluded the Franco-Soviet Treaty of Mutual Assistance, a mutual aid pact in which each promised to come to the other's defense in the event that aggression violating the Covenant of the League of Nations was suffered. Shortly thereafter, two days of consultations in Moscow between French Foreign Minister Pierre Laval and Soviet chiefs Joseph Stalin, Viacheslav Molotov, and Maxim Litvinov helped to solidify the agreement through a joint communique in which the parties agreed "not to allow their means of national defense to weaken in any respect" and which recognized France's right to "maintain her armed forces at a level consonant with her security".

The May 1935 treaty and formal communique between France and the USSR tilted the scale decisively towards a new Comintern policy for the Communist Parties of the world, casting aside the old Third Period line of "class against class" for the overthrow of the bourgeoisie in favor of a new policy of realpolitik, defending the Russian revolution by supporting mutual defense agreements between the USSR and various capitalist states. Further marking this shift in the international political line of the Comintern was the appointment of Popular Front adherent Georgi Dimitrov as new head of the Communist International. The stage was therefore set for the belated convocation of the Comintern's 7th World Congress.