Guillaume Courtois was born in Saint-Hippolyte, Doubs, in France as the son of the obscure painter Jean-Pierre Courtois. Very little is known about Guillaume’s youth but it is assumed he received his initial training 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.
The movements of the brothers Courtois are not very well documented, which has led to alternative theories. It is possible Guillaume Courtois settled in Rome by 1638 where he entered the studio of Pietro da Cortona. Here he is supposed to have supplemented his training by drawing from life and copying works of Giovanni Lanfranco and Andrea Sacchi. 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 15 June 1679. More on Guillaume Courtois