Everybody knows the characters from The Three Musketeers by Alexandre Dumas. The story was first serialised in 1844 and became a huge success and writing inspiration for generations of authors around the world.
As a historical adventure novel, The Three Musketeers mixed real characters with fictional events and stories, making difficult to truly understand where the fiction begins. Here is a very simple dossier about the characters, real people or fictional characters?
D'Artagnan: this character was in fact Charles de Batz de Castelmore d'Artagnan (around 1611-1673), a real person. He worked for Cardinal Mazarin and served as captain of the Musketeers during the reign of Louis XIV. In 1700, Gatien de Courtilz published his vision of the story of d'Artagnan, a semi-fictionalized memoirs. His works served as the model for The Three Musketeers. D'Artagnan really existed, but his legacy was in fact a historical fiction inspired by a semi-fiction.
Athos: Athos was probably freely inspired by Armand de Sillègue d'Athos d'Autevielle, a real musketeer, but the character is very fictional.
Isaac de Porthau, a gascon musketeer, served as the inspiration for the character of Porthos as well as Henri d'Aramitz, abbot and musketeer, was the basis of the character of Aramis. Both of them are fictional.
M. de Tréville/Tresville: this character was in fact Jean-Armand du Peyrer (1598-1672) from Trois-Ville.
The famous antagonist Milady de Winter is a fictional character, but Alexandre Dumas used the mention of a person named Lucy Hay in the memoirs of d'Artagnan by Gatien de Courtilz as an inspiration to create her.
Of course, main historical characters like Anne d'Autriche or Cardinal Richelieu are based on real people.