The Counter-Reformation (Latin: Contrareformatio), also sometimes called the Catholic Revival, was the period of Catholic resurgence that was initiated in response to, and as an alternative to or from similar insights as, the Protestant Reformations at the time. It was a comprehensive effort arising from the decrees of the Council of Trent.

As a political-historical period, it is frequently dated to have begun with the Council of Trent (1545–1563) and to have ended with the political conclusion of the European wars of religion in 1648, though this is controversial. However, as a theological-historical description, the term may be obsolescent or over-specific: the broader term Catholic Reformation (Latin: Reformatio Catholica) also encompasses the reforms and movements within the Church in the periods immediately before Protestantism or Trent, and lasting later.

The effort produced apologetic and polemical documents, anti-corruption efforts, spiritual movements, the promotion of new religious orders, and the flourishing of new art and musical styles. War and discriminatory legislation caused large migrations of religious refugees.

Such reforms included the foundation of seminaries for the proper training of priests in the spiritual life and the theological traditions of the Church, the reform of religious life by returning orders to their spiritual foundations, and new spiritual movements focusing on the devotional life and a personal relationship with Christ, including the Spanish mystics and the French school of spirituality. It also involved political activities and used the regional Inquisitions.

A primary emphasis of the Counter-Reformation was a mission to reach parts of the world that had been colonized as predominantly Catholic and also try to reconvert nations such as Sweden and England that once were Catholic from the time of the Christianisation of Europe, but had been lost to the Reformation. Various Counter-Reformation theologians focused only on defending doctrinal positions such as the sacraments and pious practices that were attacked by the Protestant reformers, up to the Second Vatican Council in 1962–1965.

'Counter-Reformation’ is a translation of German: Gegenreformation.

Protestant historians have tended to speak in terms of Catholic reform as part of the Counter-Reformation, itself a response to the Reformation.

In nineteenth-century Germany, the term became part of the German: Kulturkampf: ‘Counter-Reformation’ was used by Protestant historians as a negative and one-dimensional concept that stressed the aspect of reaction and resistance to Protestantism and neglected that of reform within Catholicism. The term was understandably shunned by Catholic historians. Even when the Protestant historian Wilhelm Maurenbrecher introduced the term ‘Catholic Reformation’ in 1880, German historiography remained confessionally divided on the subject. The term ‘Catholic Reformation’ appealed to Catholic historians because it offered them the possibility of avoiding the term ‘Counter-Reformation’, with its problematic connotation of a mere reaction to Protestantism. But it was rejected by Protestant historians – largely because they did not want the term ‘Reformation’ to be used for anything other than the Protestant Reformation.