Guillaume Courtois (1628 – June 15, 1679), called "Il Borgognone", was a French painter and etcher, the brother of the Jesuit painter Jacques Courtois. His working career was spent in Rome. He is also known as Guglielmo Cortese.
Like his brother, he was born in Saint-Hippolyte, Doubs in France to a painter. Together, father and sons went to Italy when Guillaume was still a child.
He painted the Battle of Joshua in the Gallery of the Quirinal Palace, the Crucifixion of St Andrew in Sant'Andrea al Quirinale, various works for the Jesuits, some also in co-operation with his brother. His last production was Christ admonishing Martha.
Encyclopaedia Britannica 1911 found that "His draughtsmanship is better than that of Jacques, whom he did not, however, rival in spirit, colour or composition." Guillaume Courtois died of gout on June 15, 1679.