In the Catholic Church, a religious order is a community of consecrated life with members that profess solemn vows. They are classed as a type of religious institute.

Subcategories of religious orders are:

• canons regular (canons and canonesses regular who recite the Divine Office and serve a church and perhaps a parish);
• monastics (monks or nuns living and working in a monastery and reciting the Divine Office);
• mendicants (friars or religious sisters who live from alms, recite the Divine Office, and, in the case of the men, participate in apostolic activities); and
• clerics regular (priests who take religious vows and have a very active apostolic life).

Original Catholic religious orders of the Middle Ages include the Order of Saint Benedict. In particular the earliest orders include the Poor Ladies (later called the Poor Clares), founded by St. Francis of Assisi in 1212]], English Benedictine Congregation (1216) and Benedictine communities connected to Cluny Abbey, the Benedictine reform movement of Cistercians, and the Norbertine Order of Premonstratensians (1221). These orders were confederations of independent abbeys and priories, who were unified through a leadership structure connected to permanent establishments.

A century later, mendicant groups like the Carmelites, the Order of Friars Minor, the Dominican Order, the Order of the Most Holy Trinity and the Order of Saint Augustine formed their Orders. As such, also the Teutonic Order may qualify, as today it is mainly monastic. These Mendicant Orders did not hold property for their Religious Communities, instead begging for alms and going where they were needed. Their leadership structure included each member, as opposed to each Abbey or House, as subject to their direct superior.

In the past, what distinguished religious orders from other institutes was the classification of the vows that the members took in religious profession as solemn vows. According to this criterion, the last religious order founded was that of the Bethlehem Brothers in 1673. Nevertheless, in the course of the 20th century, some religious institutes outside the category of orders obtained permission to make solemn vows, at least of poverty, thus blurring the distinction.