Dominic was born in Caleruega, halfway between Osma and Aranda de Duero in Old Castile, Spain. He was named after Saint Dominic of Silos. The Benedictine abbey of Santo Domingo de Silos lies a few miles north of Caleruega.
At fourteen years of age, Dominic was sent to the Premonstratensian monastery of Santa María de La Vid and subsequently transferred for further studies in the schools of Palencia. In Palencia, he devoted six years to the arts and four to theology. At some point in time he also joined Santa María de La Vid as a canon.
At the age of 24, Dominic was ordained as a priest, and subsequently joined the canonry of the Cathedral of Osma. In 1198, Diego de Acebo, the Bishop of Osma, having reformed the chapter and assigned himself as prior, made Dominic the subprior of the chapter.
In 1215, Dominic established himself, with six followers, in a house given by Peter Seila, a rich resident of Toulouse. Dominic saw the need for a new type of organization to address the spiritual needs of the growing cities of the era, one that would combine dedication and systematic education, with more organizational flexibility than either monastic orders or the secular clergy. He subjected himself and his companions to the monastic rules of prayer and penance; Bishop Foulques gave them written authority to preach throughout the territory of Toulouse.