The easiest and quickest way? Do we have to go back through Paris?

This would be spring of next year.

Thanks

No one knowns what the schedules will be almost a year from now but the quickest route between these two points is currently 4+46 with a change of trains at Versailles Chantier.

Until about November, you won't be able to look up exact timings / services, as the timetable changes in December and they won't publish it until about November. Tickets will then be sold about 3 months out, and you'll want to book any TGV legs at 90 days to secure the cheapest prices. (High speed trains in France are priced much like airline tickets, complete with budget-like options from idTGV and Ouigo!)

Unless you do something odd with slow trains, your easiest is to head from Chartres to Paris, change stations, then take a TGV down to Avignon. Well, either that, or train to Paris, RER to Marne la Vallee, then Ouigo down.

There's a handful of direct TGVs from Tours to Avignon, but getting there from Chartres isn't that easy. You could take a local train to Le Mans, then TGV to Nimes, then local train on, but via Paris looks easier than that to me!

All great information. Thanks

I am aware that we are way to early for schedules or to book tickets...but I wanted to research routes and see if my itinerary is plausible.

It the Versailles Chantier is viable that seems to be the easiest since it does not require a change of station for the connection down to Avignon. I see direct trains that are approx. 3.5 hours....