The term Augustinians, named after Saint Augustine of Hippo (354–430), applies to two separate and unrelated types of Catholic religious orders:

1) several mendicant Orders of friars, who lived a mixed religious life of contemplation and apostolic ministry and follow the Rule of St. Augustine, a brief document providing guidelines for living in a religious community. The largest and most familiar, originally known as the Hermits of Saint Augustine (O.E.S.A. - Ordo Eremitarum sancti Augustini), is now simply referred to as the Order of Saint Augustine (O.S.A.).

Two other Orders, the Augustinian Recollects and the Discalced Augustinians, were once part of the Augustinian Order under a single Prior General. The Recollect friars, founded in 1588 as a reform movement of the Augustinian friars in Spain, became autonomous in 1612 with their first Prior General, Enrique de la Sagrada. The Discalced friars became an independent religious congregation with their own Prior General in 1592, and were raised to the status of a separate mendicant Order in 1610.

St. Thomas of Villanova, O.S.A. (born Tomás García Martínez, Ciudad Real, 1488 - died Valencia, September 8, 1555), was a preacher, ascetic, writer and Spanish friar of the Order of Saint Augustine.

Thomas grew up and was educated in Villanueva de los Infantes, in the province of Ciudad Real, Spain, where his parents owned a prosperous estate; therefore the name Thomas of Villanueva. Part of the original house still stands, with a coat of arms in the corner, beside a family chapel. In spite of his family's wealth, as a young boy he often went about naked because he had given his clothing to the poor.

Even though he studied Arts and Theology at the University of Alcalá de Henares and became a professor there, he decided to enter the Augustinian order in Salamanca in 1516, and in 1518 was ordained a priest. Within the order, he held the positions of prior of the friary, General Visitor, and Provincial Prior for Andalusia and Castile. He was also a professor at the university and counsellor and confessor to the Spanish King and Holy Roman Emperor Charles V.