Ernest Gaston Joseph Solvay (16 April 1838 – 26 May 1922) was a Belgian chemist, industrialist and philanthropist.
Born at Rebecq, he was prevented by acute pleurisy from going to university. He worked in his uncle's chemical factory from the age of 21.
In 1861, he developed the ammonia-soda process for the manufacture of soda ash (anhydrous sodium carbonate) from brine (as a source of sodium chloride) and limestone (as a source of calcium carbonate). The process was an improvement over the earlier Leblanc process.
He founded the company Solvay & Cie and established his first factory at Couillet (now merged into Charleroi, Belgium) in 1863 and further perfected the process until 1872, when he patented it. Soon, Solvay process plants were established in the United Kingdom, the United States, Germany and Austria. Today, about 70 Solvay process plants are still operational worldwide.
The exploitation of his patents brought Solvay considerable wealth, which he used for philanthropic purposes, including the establishment in 1894 of the "Institut des Sciences Sociales" (ISS) or Institute for Sociology at the Free University of Brussels (now split into the Université Libre de Bruxelles and the Vrije Universiteit Brussel), as well as International Institutes for Physics and Chemistry. In 1903, he founded the Solvay Business School which is also part of the Free University of Brussels. In 1911, he began a series of important conferences in physics, known as the Solvay Conferences, whose participants included luminaries such as Max Planck, Ernest Rutherford, Marie Curie, Henri Poincaré, and (then only 32 years old) Albert Einstein. A later conference would include Niels Bohr, Werner Heisenberg, Max Born, and Erwin Schrödinger.
He was two times elected to the Belgian Senate for the Liberal Party and appointed Minister of State at the end of his life. Solvay, New York and Rosignano Solvay, the locations of the first Solvay process plants in the United States and in Italy, are also named after him.
Solvay died at Ixelles and is interred there in the Ixelles Cemetery.