Augustinians are members of several religious orders that follow the Rule of Saint Augustine, written in about 400 AD by Augustine of Hippo. There are two distinct types of Augustinians in Catholic religious orders dating back to the 12th–13th centuries:Various congregations of Canons Regular also follow the Rule of Saint Augustine, embrace the evangelical counsels and lead a semi-monastic life, while remaining committed to pastoral care appropriate to their primary vocation as priests. They generally form one large community which might serve parishes in the vicinity, and are organized into autonomous congregations. Several orders of friars who live a mixed religious life of contemplation and apostolic ministry. The largest and most familiar is the Order of Saint Augustine (OSA), founded in 1244 and originally known as the Hermits of Saint Augustine (OESA). They are commonly known as the Austin Friars in England. Two other orders, the Order of Augustinian Recollects and the Discalced Augustinians, were once part of the OSA under a single prior general. The Recollects, founded in 1588 as a reform movement in Spain, became autonomous in 1612. The Discalceds became an independent congregation in 1592, and were raised to the status of a separate mendicant order in 1610.

The Rule of Saint Augustine, written in about the year 400, is a brief document divided into eight chapters and serves as an outline for religious life lived in community. It is the oldest monastic rule in the Western Church.