The primary reason for the Protestant Reformation in Europe, which began in the early 16th century, was the widespread discontent with the Catholic Church's practices and abuses, particularly the sale of indulgences. Reformers like Martin Luther criticized the Church's corruption, the excesses of the clergy, and the need for a return to biblical teachings. Luther's "95 Theses" galvanized support for reform, leading to the emergence of various Protestant denominations. The Reformation challenged the religious, political, and social order of the time, ultimately contributing to significant changes across Europe, including the rise of secularism and modern national identities.