Guillaume François Rouelle (15 September 1703 – 3 August 1770) was a French chemist and apothecary.
In 1754 he introduced the concept of a base into chemistry, as a substance which reacts with an acid to give it solid form (as a salt).
He is known as l'Aîné (the elder) to distinguish him from his younger brother, Hilaire Rouelle, who was also a chemist and known as the discoverer of urea.
He started a public course in his laboratory in 1738 where he taught many students among whom were Denis Diderot, Antoine-Laurent de Lavoisier, Joseph Proust and Antoine-Augustin Parmentier.
He was elected a foreign member of the Royal Swedish Academy of Sciences in 1749.