Throughout history, Spain has been one of the countries known as the defender of Catholic Christianity. The Spanish Catholicism was able to expand the realm of Christianity in various countries, especially Latin America, by empowering Christian kings. Political, social, and religious necessities require that Latin American Christianity be recognized, and this recognition would not be possible without an understanding of Spanish Christianity. This article examines the nature and characteristics of Spanish Catholic Christianity from the beginning to the time of the conquest of Latin America in the 15th century. During this period, Catholic Christianity went through three periods, including: the arrival in Spain; the Catholicization of Christianity in Spain and the period of the establishment of Catholic Christianity. Catholic Christianity entered Spain with a Roman nature and, with the struggle against Aryan Christianity, spread to all parts of Spain. Finally, in the 15th century, with the help of Catholic kings, Catholicism became an undisputed Christian and religious power in Spain and around the world.