Bonjour, we are landing on a Monday morning at CDG, can we take a train directly from CDG to Chartres?
No direct trains for CDG to Chartres.
Take RER B train from CDG airport into Paris, transfer at Denfert-Rochereau station to Metro line 6, direction Charles de Gaulle-Etoile, until Montparnasse Bienvenue station, then walk to Gare Montparnasse.
From Gare Montparnasse there are direct Paris - Chartres trains serviced by Ter. Cost per ticket is 18.40€ one-way. You can use Ter ticket vending machines or buy the ticket from the Grandes Lignes / SNCF ticket offices.