The Reformation had a profound impact on Catholicism in Europe, leading to significant theological, political, and social changes. Initiated in the early 16th century by figures like Martin Luther and John Calvin, it challenged the authority of the Catholic Church and prompted the establishment of Protestant denominations. The Reformation criticized practices such as indulgences and emphasized personal faith and scripture over tradition. In response, the Catholic Church launched the Counter-Reformation, addressing internal corruption and reaffirming core doctrines. This period resulted in a fragmented Christianity, increased religious conflict, and laid the groundwork for modern secularism and diverse faith expressions in Europe.