The Hôtel Solvay (French: Hôtel Solvay; Dutch: Hotel Solvay) is a large historic town house in Brussels, Belgium. It was designed by Victor Horta for Armand Solvay, the son of the chemist and industrialist Ernest Solvay, and built between 1895 and 1900, in Art Nouveau style. It is located at 224, avenue Louise/Louizalaan, not far from the Hôtel Max Hallet, another remarkable Art Nouveau building by Horta.

Together with three other town houses of Victor Horta, including Horta's own house and workshop, it was added to the UNESCO World Heritage list in 2000 as the core of epoch-making urban residences that Horta designed before 1900.^[2]

The Hôtel Solvay was designed and built by Horta, between 1895 and 1900, to serve as a private residence for Armand Solvay, the son of the chemist, industrialist and philanthropist Ernest Solvay. For this wealthy patron, Horta could spend a fortune on precious materials and expensive details. He designed every single detail: furniture, carpets, light fittings, tableware and even the doorbell. He used expensive materials such as marble, onyx, bronze, tropical woods, etc. For the decoration of the staircase, he cooperated with the pointillist painter Théo van Rysselberghe.

The Hôtel Solvay and most of its content remained intact thanks to the Wittamer family. They acquired the house in the 1950s and did the utmost to preserve and restore this magnificent dwelling. The house is still private property and can only be visited by appointment and under very strict conditions. On 23 January 2021, the building began to operate as a museum,^[3] and currently accept visitors five days a month on selected timeslots.

Major renovation works to the Hôtel Solvay's façade began in March 2022,^[4] and its exterior is currently entirely covered in scaffolding.^[5] While the scaffolding was planned to be dismantled in time for the Brussels Art Nouveau Festival in summer 2023,^[6] this deadline was ultimately missed; the renovations' current estimated completion date is unknown.

The UNESCO commission recognised the Hôtel Solvay as UNESCO World Heritage in 2000, as part of the listing 'Major Town Houses of the Architect Victor Horta':

The four major town houses—Hôtel Tassel, Hôtel Solvay, Hôtel van Eetvelde, and Maison & Atelier Horta—located in Brussels and designed by the architect Victor Horta, one of the earliest initiators of Art Nouveau, are some of the most remarkable pioneering works of architecture of the end of the 19th century. The stylistic revolution represented by these works is characterised by their open plan, the diffusion of light, and the brilliant joining of the curved lines of decoration with the structure of the building.^[2]

• Design of interior decoration by Horta
• Façade
• Entrance
• Doorbell
• Central salon
• Main stairs to first floor
• Stairs between first and second floors

• Art Nouveau in Brussels
• History of Brussels
• Culture of Belgium
• Belgium in the long nineteenth century