The cowl (from the Latin, cuculla) is a long, outer garment, with wide sleeves, worn by Catholic monks when participating in the liturgy. Developed in the Middle Ages as a more practical alternative to wearing a cloak, they became the formal garment for those in monastic life. They were worn to give warmth to people who often spent long hours in unheated and drafty churches.

They are most commonly bestowed upon the monk at the time of his making solemn, or lifetime, vows. They are generally worn in conformity with the color of the monk's tunic, with the Benedictines wearing black, while other groups which also follow the Rule of St. Benedict, e.g., the Camaldolese and Cistercians wear some form of white. The garment, without a hood, is also worn by nuns, in the same manner.

It should be noted that those orders which are not part of the Benedictine tradition, e.g., the Carthusians, do not make use of this garment.