Menhir de Chantecoq ou Mère-aux-Cailles, Neolithic menhir in Ymeray, France.

The Menhir de Chantecoq is a weathered, heavily fissured slab of conglomerate about 3.0 m high, standing in the hamlet of Pont-sous-Gallardon southeast of Bailleau-Armenonville. Its irregular form has a rounded top and a wider lower section, with a single dark circular hole piercing the lower left-center. The grey and brown stone, patched with green moss, is covered in graffiti, including a large black-and-white bubble-letter tag.

The Menhir de Chantecoq is a Neolithic standing stone in the hamlet of Pont-sous-Gallardon, near Bailleau-Armenonville. It stands close to the Chantecoq polissoirs and the largely destroyed Chantecoq dolmen. The stone is listed in the Base Mérimée of the French Ministry of Culture as a classified historical monument; the sources give no date for this protection.

Locals know the stone as La Mère aux Cailles, "the mother of quails", alongside the name Chantecoq; both are popular nicknames rather than recorded legends. It stands in the hamlet of Pont-sous-Gallardon, near the largely destroyed Dolmen de Chantecoq and the Chantecoq polishing stones, so the three prehistoric monuments are seen together.

The menhir stands in the hamlet of Pont-sous-Gallardon, southeast of Bailleau-Armenonville and northeast of Chartres, in Eure-et-Loir. It is reached from the local lanes of the hamlet, and the surrounding land is private, so keep to the path. The nearby Chantecoq polissoirs and the largely destroyed dolmen can be seen on the same outing.

The stone is a 3 m slab of conglomerate, not granite, and its surface is heavily weathered and fissured. A single round hole pierces its lower left side, and spray-painted tags cover the middle, including a large black-and-white bubble-letter piece. The menhir stands near the largely destroyed Dolmen de Chantecoq and the Chantecoq polissoirs.