Enclosed religious orders are religious orders whose members strictly separate themselves from the affairs of the external world. The term cloistered is synonymous with enclosed. In the Catholic Church, enclosure is regulated by the code of canon law, either the Latin code or the Oriental code, and also by the constitutions of the specific order. It is practised with a variety of customs according to the nature and charism of the community in question. This separation may involve physical barriers such as walls and grilles, with entry restricted for other people and certain areas exclusively permitted to the members of the convent. Outsiders may only temporarily enter this area under certain conditions. The intended purpose for such enclosure is to prevent distraction from prayer and the religious life and to keep an atmosphere of silence.

When referring to Roman Catholic religious orders, the term Second Order refers to those communities of contemplative cloistered nuns which are a part of the religious orders that developed in the Middle Ages.