The Tironensian Order or the Order of Tiron was a medieval monastic order named after the location of the mother abbey in the woods of Thiron-Gardais in Perche, some 35 miles west of Chartres in France). They were popularly called "Grey Monks" because of their grey robes, which their spiritual cousins, the monks of Savigny, also wore.

Perche is a former province of France, known historically for its forests and, for the past two centuries, for the Percheron draft horse breed. Until the French Revolution, Perche was bounded by four ancient territories of northwestern France: the provinces of Maine, Normandy, and Orléanais, and the region of Beauce. Afterwards it was absorbed into the present-day departments of Orne and Eure-et-Loir, with small parts in the neighboring departments of Eure, Loir-et-Cher, and Sarthe.