Catholic Action is a movement of lay people within the Catholic Church which advocates for increased Catholic influence on society. Catholic Action groups were especially active in the nineteenth century in historically Catholic countries under anti-clerical regimes, such as Spain, Italy, Bavaria, France, and Belgium.

Catholic Action is not a political party in and of itself; however, in many times and places, these movements have engaged in political activities. Since World War II, the concept has often been supplanted by Christian Democrat parties that were organised to combat Communist parties and promote Catholic social justice principles in places such as Italy and West Germany.

Catholic Action generally includes various subgroups for youth, women, workers, and so on. In the postwar period, the various national Catholic Action organizations for workers formed the World Movement of Christian Workers, which remains active today as a voice within the Church and in society for working class Catholics.

The Catholic Action movement has its beginnings in the latter part of the 19th century as efforts to counteract a rise in anti-clerical sentiment, especially in Europe.

A variety of diverse groups formed under the concept of Catholic Action. These include the Young Christian Workers, the Young Christian Students; the Cursillo movement, RENEW International; the Legion of Mary; Sodalities; the Christian Family Movement; various community organizing groups like COPS (Communities Organized for Public Service) in San Antonio, and Friendship House in Harlem, an early influence on Thomas Merton.

Around 1912, as a curate in a parish in Laeken, on the outskirts of Brussels, Joseph Cardijn, who dedicated his ministry to aid the working class, founded for the young seamstresses a branch of the Needleworkers' Trade Union. In 1919 he founded the Young Trade Unionists. In 1924, the name of the organization was changed to "Jeunesse Ouvrière Chrétienne", the Young Christian Workers. JOC grew throughout the world; its members were often known as "Jocists" (the movement was often called "Jocism"). By 1938, there were 500,000 members throughout Europe; in 1967, this had increased to 2,000,000 members in 69 countries.

In 1934, Adolf Hitler ordered the murder of Erich Klausener, head of a Catholic Action group in Nazi Germany, during the Night of the Long Knives.^{[citation needed]}

Pope Paul VI commended those who are "fighting for Christ in the ranks of Catholic Action and in the other associations and activities of the apostolate" in his first encyclical letter, Ecclesiam suam, linking their actions with the dialogue inside and outside the church which he saw as the work of the Second Vatican Council.