The Reformation had an enormous impact on European politics. Previously, the Pope had been both a powerful temporal, as well as spiritual, ruler. Yet, the Reformation directly challenged not just his spiritual authority, but also his political authority as a prince. Kings, princes, and other rulers who embraced the Reformation saw an opportunity to divest themselves of their onerous responsibilities towards the Pope. In particular, they found they no longer had to send large sums of money to Rome, as tribute for a Church whose teachings they now rejected.

In the Reformation's wake, political power in Europe became more thoroughly secularized, with rulers such as Henry VIII of England declaring themselves heads of their respective national churches. This greatly altered the balance of power in Europe and led to the break-up of Western Christendom. Now there was no longer one Church, but several smaller ones.

In the ensuing disorder and upheaval, only a strong secular ruler in each respective territory was thought capable of preventing a slide into outright chaos. The parlous state of civil society, combined with the attack on the Catholic Church, represented by the Reformation, led to secular rulers accruing greater powers over their lands and subjects, significantly weakening the Papacy's authority in the process.

When Martin Luther posted his Ninety-five Theses to the door of a church, he was inviting a debate over a spiritual practice, the selling of indulgences, in the Catholic Church. He had no way of knowing it would result in such a tremendous spiritual and political conflict in Europe. For centuries, the power and authority of the pope had grown in Europe. Popes were doing more than just offering spiritual leadership. They were living like kings. Popes launched wars, made treaties, lived in luxury, and even fathered illegitimate children. Both Pope Julius and Pope Leo used the money collected from indulgences to pay for luxurious improvements to the Vatican. So when Luther began asking questions about the authority of the church, it was the beginning of a threat to the political power of the Holy Roman Empire. In 1520 Pope Leo X condemned Martin Luther and ordered that all of his writings be burned. As Germany continued to pull further and further away from the pope and from Rome, the Holy Roman Emperor, Charles V, called the Diet of Worms. This was another attempt to keep the empire together and squash any rebellion. The attitude of spiritual rebellion against the church in Germany led to a demand for not only spiritual reformation, but also social and economic reformation. Knights rose up against rulers, and peasants rose up against landowners. Finally, in 1529 at the Diet of Spires, the princes of the Holy Roman Empire were given the right to decide if their region would follow the pope or Luther. The princes who followed Luther were subjected to much more limits to their freedom. For this unfairness they protested. This is where they began to be referred to as Protestants, from the Latin pro testans which means "bearing witness."

The Protestant Reformation had far reaching political consequences for Western Europe, perhaps more far reaching than were its religious consequences.

Germany, where the Reformation began was part of the Holy Roman Empire. The Holy Roman Emperor considered it his mandate to protect the Roman Catholic Church and ensure its supremacy. With the outbreak of the Reformation, a number of German princes determined that they could separate themselves from the Emperor's control by allying with the Protestant movement, and did so. In France, civil wars frequently broke out between Calvinist (Huguenot) forces and Catholic forces loyal to the King. As a result, a number of catastrophic wars broke out in Europe, primarily the Wars of Religion and the Thirty Years War. Both were fought over a combination of religion and politics. In France, Huguenots were lured to a meeting on St. Bartholomew's day with Catholics to discuss a peace settlement and told not to bring their weapons. They complied and were slaughtered in the St. Bartholomew's Day Massacre.

Interestingly, the Wars of Religion ended with an agreement that the ruler of each area would determine that area's religion.