Traveling from Disneyland Paris to Versailles

They're both outside the city, on opposite sides of Paris, so it's going to take a while. The fastest way, since it doesn't get stuck in traffic, is to take the RER line A (red on maps) from DLP into Paris, to the St. Michel-Notre Dame stop. There, change to RER line C (yellow on maps). You want line C5, going to Versailles Rive Gauche (closest stop to the Chateau). As each train pulls into the station, a board lights up the stops that particular train is stopping at. Versailles Rive Gauche will be the last stop on your train.

To get back take RER C to St. Michel-Notre Dame. There, change to RER line A. You want line A4, with the last stop of Marne-la-Vallée Chessy.

I wouldn't be surprised if your hotel had some form of shuttle to Versailles, which probably will cost more, but which you may prefer as it would be a "one seat ride."

EDIT: OOPS!!! I was mixing up my lines - please disregard this post!

Sorry, the RER line A does NOT stop at St Michel-Notre Dame and there is no interchange between A and C in central Paris. Probably the easiest route is to get out of Line A at Gare de Lyon, walk over the river to the nearby Gare d'Austerlitz, and take Line C from there. (There are also buses between Gare de Lyon and Gare d'Austerlitz, but it's such a short distance that walking may well be quicker than waiting for a bus.) If you don't want to walk at all, though, you'd have to get out of Line A at Chatelet and take Line B to St Michel-Notre Dame.

We have done it twice from there - the easiest is to take the RER A to Chatelet - transfer to RER B to St Michel/Notre Dome - transfer to RER C to Versailles Rive Gauche. it takes about two hours one way or an hour to drive.

Here is a route planner for RATP

Here is an interactive map

Philip is right - I was mixing up my RER lines!

Please disregard my post. Sorry!

Thanks, all.