Round trip transportation -- Paris to Versailles

RER C from any of many stations along the left bank of the Seine. Cost is 3.65 EUR per person each way. Station you are going to is Versailles Chateau - Rive Gauche. Trains about every 15 minutes, takes 47 minutes to get there, at least from St Michel-Notre Dame.

Here is a schematic of the Paris rail network. RER C is the yellow line following the south bank of the Seine with all the stations and Metro connections. Versailles Chateau - Rive gauche in the lower left of the map.
https://www.ratp.fr/en/plan-rer

Thank you Sam!

Be prepared for a packed RER, especially coming back. Recently I sat on the stairs, as we were like the aying "sardines in a can." That's when it is a very good time to wear your mask on public transport.

Another possibility is taking the metro or RER A to La Defence, and then taking the L line to Versailles Rive Droit. Follow Sam's link, and click on the Transilien tab, then on the L line.

What I like about this route is the view looking East back into Paris and the Eiffel Tower

So good to know all of this, thank you for the responses.

You can use Google maps for this in France as well - and if you don't want to pay for an internet connection while there, you can use it here and screen shot or copy the directions or print.

beware if you are going between mid july and mid august, that line RER C will be closed for the infamous annual works. So from St Lazare or Montparnasse or La Défense are best during the summer works

Great information to pass on to others! We actually completed this trip today. The train from Versailles back to Paris was incredibly easy to navigate and very economical, and we only encountered the "packed like sardines" trains when we were back in Paris so we just walked the 12 minutes to our apartment. Many thanks to all who contributed to this posting. It was such a wonderful encouragement to us and we had a fabulous time in Versailles.