The Protestant Reformation took place all over Western Europe, though it took place most strongly in the northern parts of that area.
The most famous part of the Reformation was the part that took place in Germany. Martin Luther was German and he was the one who started the process that would become the Reformation. The Reformation also took place in Switzerland, which is where John Calvin preached. It also took place in England, where Henry VIII set up the Church of England in place of the Catholic Church.
The process that we now call the Reformation started in Germany but it affected all of Western Europe.
The Protestant Reformation was not a single event that happened on one particular day in one specific location. The changes in beliefs, practices, and attitudes that became collectively known as the Protestant Reformation developed and spread throughout Europe during much of the sixteenth century.
Martin Luther's objections to the Roman Catholic Church's practice of selling indulgences became the starting point of the Reformation. He intended to simply start a discussion of this practice with his "The Ninety-Five Theses", traditionally thought to have been nailed to the door of the All Saints Door in Wittenberg, Germany in 1517. The debate never took place, but his ideas quickly spread with the help of the relatively newly invented printing press.
Swiss theologian Huldrych Zwingli agreed with Luther's objections to the sale of indulgences and went on to set out more disagreements with Roman Catholic Church practice. Zwingli felt Luther did not move far enough away from Catholic liturgy and behavior and quickly led his followers away from the Lutheran branch of protestants to form their own church. Some of those followers later became the Anabaptist Church.
John Calvin, born in France but active as a reformer in Switzerland, was influenced by Zwingli's work but did not agree with all his positions. Calvin's work led to the development of Calvinism, which provided the basis for the development of the Reformed and Presbyterian Churches.