Train Travel in France

https://en.oui.sncf/en/tgv
Since SNCF runs the trains, they should be your starting point to see what is available.

None are "high speed", they are InterCities trains, but some of them are indeed non-stops.

Seat61 is a good place to get basic info about trains in Europe, including tips on the best way to buy tickets from the US:
https://www.seat61.com/France.htm

Check out www.seat61.com for all you'll need to know about train travel or ferry travel across Europe.

The high speed trains are the TGVs. Book 3 mos or so out, more in summer, for the best deals. It only takes 45 minutes Paris to Reims by TGV and 3.5 hours by Thalys high speed train to Amsterdam and about the same by TGV to Nice.

As suggested, Seat61.com is extremely helpful.

I'm a fan of loco2.com - very user friendly, with no added booking fees.

https://loco2.com/

hey hey linda
i've used trainline.com several times. user friendly to me. some small fees may occur which are okay for me.
aloha

Seat61 recommends using Loco2.com. I did when i bought TGV tickets last week - super fast and easy on Loco2.com

I would also suggest using Trainline.com as their website is very easy to use and they also have a smartphone App. Registration on the site is required, including payment details, but once that's done the process is very easy. They sell tickets not only for trains in France, but also Germany, Italy, Spain, UK and other countries. As mentioned earlier, there may be some small fees for ticket purchase, but I don't find that to be a problem.

Another fan of Trainline. Just got back from using it in France and Spain.

Our first trip is Paris to Rouen. Are there nonstop high speed trains available?

Non stop in the context of trains means that the train does not make any intermediate station stops between where you join it and where you leave it. If you mean, "do I have to get off my train and change onto another one somewhere along the way", that would be a change or a connection. If the train you are on goes straight through and you don't need to move before the end, that would be a direct train.

The references given previously to The Man in Seat 61 are really good - I strongly suggest that you visit there and have a read. He is a man who previously worked with the railways, and his pages are comprehensive yet easy and fun to read, with lots of pictures and first hand knowledge, an excellent source of clear, easy to understand information. He writes in such a way that both experienced riders of trains and people new to train riding benefit.

In your particular example, Paris to Rouen, there are around 1 or 2 trains an hour - with the usual French gaps - with most taking 1:12 or 1:31. Other routings can be created, some taking much longer, but unless you want the round-about routings you can take one of the 1:12 or 1:31 duration trains. If you do, they are as said above InterCities normal trains, not the TGV super fast trains, but 1:12 or 1:31 are pretty fast anyway. They have no changes so are direct.

You join at Paris St Lazare station (there is a different station in Paris depending on which direction the train is going - for Rouen it is St Lazare) and the 1:31 train will stop for passengers at Mantes La Jolie, Vernon(Eure) (near Giverny for Monet's Garden),
Gaillon Aubevoye, Val-de-Reuil, and Oissel before it gets to Rouen-Rive-Droite. Rouen-Rive-Droit is its final destination and everybody left on board will get off.

If you take the faster 1:12 train it doesn't make any intermediate stops - Rouen-Rive-Droit is the first stop. The train is actually a longer distance train heading to Le Havre further down the coast, so for that train the screens will say Le Havre with a stop at Rouen.

It sounds worse than it is.

I hope that simplifies it for you.

Thanks to all who answered my query about train travel. I have a follow-up question. Our trip is less than two months away and when I try to get train tx at loco2 I get a message that they are not selling tickets yet for that date; they open for ticket sales two months in advance. And now we are within that window and they are not selling tickets. Then I went to Trainline and it looked like I could buy tickets at that site. Does that make sense? Thanks!