The Third Force (Troisième Force) was a French coalition during the Fourth Republic (1947-1958) which gathered the French Section of the Workers' International (SFIO) party, the Democratic and Socialist Union of the Resistance (UDSR) centre-right party, the Radicals, the Christian democrat Popular Republican Movement (MRP) and other centrist politicians, opposed both to the French Communist Party (PCF) and the Gaullist movement. The Third Force governed France from 1947 to 1951, succeeding the tripartisme alliance between the SFIO, the MRP and the PCF. The Third Force was also supported by the conservative National Centre of Independents and Peasants (CNIP), which succeeded in having its most popular figure, Antoine Pinay, named President of the Council in 1952, a year after the dissolving of the Third Force coalition.
The Third Force was organised after the dismissal of vice-premier Maurice Thorez and four others Communist ministers from Paul Ramadier's government during the May 1947 crisis. The May 1947 crisis can be summarized as: "The Communists' refusal to continue support for the French colonial reconquest of Vietnam on one hand and a wage-freeze during a period of hyperinflation on the other were the immediate triggers to the dismissal of Thorez and his colleagues from the ruling coalition in May 1947". Nevertheless, the heterogeity of the Third Force increased the ministerial instability. Although it kept its majority after the 1951 legislative election, in part due to the change of voting system, it split over economic policies, laïcité and the financing of denominational schools. The Socialists left the cabinet and the following governments were formed by centre and centre-right parties: the Radical Party, the UDSR, the MRP and the National Centre of Independents and Peasants (CNIP)
The idea of reviving a Third Force between the centre-left and the centre-right in France has been raised periodically ever since. The Socialist Gaston Defferre and the Radical Jean-Jacques Servan-Schreiber advocated such an alliance in the 1960s, culminating in Defferre's disastrous candidacy in the French presidential election, 1969. Presidents Valéry Giscard d'Estaing and then François Mitterrand unsuccessfully tried to revive the Third Force, the latter doing so in a sense by pursuing a policy of "ouverture" toward the UDF after the failure of the Socialists and their allies to gain an outright majority in the French legislative election, 1988. However, each time, the most important right-wing party, the Rally for the Republic (RPR), opposed itself to such an alliance. This strategy is now followed by François Bayrou and the Democratic Movement (MoDem), a centrist party.