Trappist beer is brewed by Trappist monks. Thirteen Trappist monasteries—six in Belgium, two in the Netherlands, and one each in Austria, Italy, England, France, and Spain— produce beer, but the Authentic Trappist Product label is assigned by the International Trappist Association (ITA) to just ten breweries which meet their strict criteria. As of 2021, Achel is no longer recognized as a Trappist brewery because it does not have any monks.

The Trappists, officially known as the Order of Cistercians of the Strict Observance and originally named the Order of Reformed Cistercians of Our Lady of La Trappe, are a Catholic religious order of cloistered monastics that branched off from the Cistercians. They follow the Rule of Saint Benedict and have communities of both monks and nuns that are known as Trappists and Trappistines, respectively. They are named after La Trappe Abbey, the monastery from which the movement and religious order originated. The movement first began with the reforms that Abbot Armand Jean le Bouthillier de Rancé introduced in 1664, later leading to the creation of Trappist congregations, and eventually the formal constitution as a separate religious order in 1892.