Hôtel Montesquiou-Fezensac, Private mansion in 7th arrondissement, Paris, France.

Hôtel Montesquiou-Fezensac is a private mansion at 20 rue Monsieur in the 7th arrondissement of Paris, built in 1781. Its street side is masked by a large modern office block, while the garden facade, visible from the boulevard des Invalides, shows pale beige stone with flat pilaster strips between tall rectangular windows, each upper window fitted with a low black metal guard rail. Only part of the interior decoration survives.

Built in 1781 by Alexandre-Théodore Brongniart for Anne-Pierre de Montesquiou-Fezensac, first equerry to the Count of Provence, near that prince's stables. In 1798 it passed to his son Pierre, grand chamberlain of the Empire, whose wife, known as "maman Quiou", was governess to the King of Rome. From 1851 to 1938 the Benedictines of Perpetual Adoration held it, adding a neo-Gothic cloister and chapel. Bought by the State in 1938, it long housed the Ministry of Cooperation; Chinese investors bought it in 2008, and in 2012 the Chinese State acquired it, installing the embassy chancery there in April 2017.

The Benedictines of Perpetual Adoration of the Most Holy Sacrament owned the house and grounds from 1851 to 1938 and added a neo-Gothic cloister and chapel. Catholic intellectuals knew them as the "bénédictines de la rue Monsieur". Joris-Karl Huysmans lodged in a small flat on the courtyard in 1901-1902.

The mansion is not open to the public: since April 2017 it has housed the chancellery of the Chinese embassy, and the street side is masked by a large office block. The 18th-century garden facade, however, can be seen from the boulevard des Invalides. The building is at 20 rue Monsieur in the 7th arrondissement.

The 2008 sale to Russian investors was for 147 million euros. In 2012 the Chinese state bought the mansion and, after five years of works, installed the chancery of its embassy there in April 2017. The garden front can be seen from the boulevard des Invalides.