Hôtel de Seignelay, Private mansion in Invalides, France.

The Hôtel de Seignelay stands at 80 rue de Lille, entered through a monumental portal flanked by two guard pavilions. Its main ashlar facade, aligned with the portal, carries carved mascarons and rises five levels, from a half-buried basement to a top floor under a mansard roof. A 444 m² paved courtyard lies behind, and a 1842 three-storey wing links the house to the street.

The mansion was built in 1713 by architect Germain Boffrand for Charles Colbert, grandson of the influential minister Jean-Baptiste Colbert. Over the centuries, ownership changed hands multiple times and the building underwent various interior modifications.

The mansion's name comes from Charles Léonor Colbert de Seignelay, grandson of Louis XIV's minister, who bought it in 1718. In 1801 the engineer Philippe Lebon demonstrated his Thermolampe lighting and heating system here. A stele in the garden marks where Coco, said to be Marie-Antoinette's last dog, is buried; Vincent Noce disputes this, calling it a spaniel that comforted the Dauphin at the Temple.

The building experienced fire damage in 2022 and is currently undergoing restoration to preserve its historical features, particularly the surviving grand staircase. Visitors should check current access conditions before planning a visit, as restoration work may affect viewing opportunities.

A stele in the garden, reached from 21 quai Anatole-France, marks where Coco, said to be Marie-Antoinette's last dog, is buried. Vincent Noce disputes this, arguing the spaniel was the one that comforted the Dauphin at the Temple and was taken to Vienna after 1795.