Ensemble castral du Montellier, Medieval castle in Le Montellier, France.

The Ensemble castral du Montellier is a brick castle complex in Le Montellier, one kilometre north of the village. Its oldest visible parts date from the 14th century: a cylindrical keep on an artificial conical mound, and to the east a trapezoidal main building on a raised platform flanked by two round towers, with false braies at the wall bases. The outer wall, built around 1330, is fronted by a moat and flanked by square towers enclosing a large lower courtyard; a ceremonial hall and a chapel stand against its south side.

The castle and its motte, or poype, are first mentioned in 1227, when the Montellier family held the land as vassals of the lords of Thoire-Villars. Humbert V de Thoire-Villars rebuilt the fortress and gave it to his son Jean de Villars on 9 March 1331; the outer wall dates from around 1330. The lordship was raised to a marquisate on 1 April 1583 by Charles-Emmanuel, Duke of Savoy, for Jacqueline de Montbel d'Entremont, and the castle was modified in the 16th and 17th centuries.

The lordship of Montellier was raised to a marquisate on 1 April 1583 by Charles-Emmanuel, Duke of Savoy, for Jacqueline de Montbel d'Entremont. The title passed with the estate through the Entremont and Chevriers families until Anne-Sylvie-Raymonde de Chevriers sold the fief in 1781 for 450,000 livres to Antoine Greppo, a royal advocate whose descendants still own the site.

The site is best explored on foot by walking around the outer walls and moat to take in the full layout. Sturdy footwear is recommended since the grounds are uneven and some paths around the complex remain natural and unpaved.

The cylindrical keep stands on an artificial truncated-cone mound on the attack side, while the trapezoidal main building behind it rests on a raised platform flanked by two round towers. The outer wall, built around 1330, is fronted by a moat and flanked by square towers enclosing a large lower courtyard.