Answer: Protestantism
Explanation: It all began with the disagreement and differing views of German Catholic priest Martin Luther, who noted a number of irregularities regarding practices and some fundamental religious issues within the Catholic Church. Thus, he proposed the famous 95 theses concerning corruption and irregularities within Catholicism. Some believe that in 1517, when Martin Luther proposed his 95 theses, the beginning of the Protestant Reformation. The Catholic Church strongly opposed Luther's intention to reform the Church, and he was excommunicated from the Catholic Church, after which he began work and action on what became the Protestant Church. It is also the first major, significant separation from the Roman Catholic Church.