thumb|240px|Presumed self-portrait
Guillaume Courtois () or italianized as Guglielmo Cortese, called Il Borgognone or Le Bourguignon ('the Burgundian'), (1628 – 14 or 15 June 1679) was a Free Burgundian-Italian painter, draughtsman and etcher. He was mainly active in Rome as a history and staffage painter and worked for high-level private patrons as well as large public commissions. He was a skilled portraitist, manifesting realistic sensitivity and a peculiar expressiveness. He left a large number of preparatory drawings which testify to his productivity.
Life
Guillaume Courtois was born in Saint-Hippolyte (Free County of Burgundy), Holy Roman Empire, as the son of the obscure painter Jean-Pierre Courtois. His two brothers Jacques (Giacomo Cortese) and Jean-François also became painters. Very little is known about Guillaume's youth and training. It is assumed that he received his initial art classes from his father. The father and his sons went to Italy circa 1636 when Guillaume was still a child. They travelled to Milan, Bologna, Venice, Florence and Siena. Another view of the movements of the brothers that has gained support with modern scholars is that Guillaume and Jacques remained together until the later 1640s and that Guillaume Courtois only came under the influence of da Cortona when he worked under him in 1656.
Guillaume Courtois spent most of his active life in Rome, where he died of gout on 14 or 15 June 1679. He collaborated with other artists on genre paintings. Some figures painted by Courtois in this Palace were previously attributed to Mola.
In 1661, he painted an Assumption for the church of San Tommaso da Villanova in Castelgandolfo in Ozzola.
In his mature work, he further showed the influence of Carlo Maratta, an artist who fused the Baroque and Classicist styles. This is reflected in the sweet faces of the female figures in works such as the Madonna of the Rosary for the St. George Church in Monte Porzio Catone made in 1666 on a commission by prince Giovanni Battista Borghese. He also collaborated frequently on public works with Bernini, who admired his work and recommended him for commissions, and Carlo Maratta.