Paris side trip?

Is this your first trip to Paris? If yes, I would consider the Montmartre are to be too far out of the way. Staying close to the river in the 4th, 5th or 6th arrondisment will keep you more central. As for how much time you have, if you stay for 9 nights it will be 8 full days. That seems like a long time, but in my opinion it is not. It really depends on your interests and travel style. If you want to go to Normandy you will need to spend at least two nights there to give you a full day of touring. Bayeaux is a good base and tours leave from there. There are many excellent tour companies. We had a great tour with Overlord. https://www.overlordtour.com/. If you choose to do this you will spend much of two days traveling to and from Normandy. I suggest a good guidebook to give you more information about what to see and do, then come back here if you have specific questions. The Rick Steves guide books are full of practical information.

jores,
Any other must-dos in Paris? Well, a months's worth of things come to mind. Check any guidebooks on Paris for ideas. Here's are a few: Eiffel Tower, Notre Dame Cathedral, Ste. Chappelle, the Invalides with Napoleon's Tomb, the Cluny Museum, Musee d'Orsay, the Orangerie, Arc de Triomphe, Rodin Museum (gardens especially), strolling along the Seine and checking out the bouquinistes, an organ concert at Ste. Sulpice church, or a concert at any number of locales, Opera Garnier, Dept. stores such as Samaritaine or Galeries Lafayette, Cathedral St. Denis (burial place of many French monarchs), Luxembourg Gardens. the Tuileries, a boat ride on the Seine, Pere Lachaise cemetery, Pompidou Center, a huge number of other museums with varying themes, and enjoying a coffee or aperitif at a cafe and watching Paris be Paris.

When you want to get out of the city, just for the day, reasonable day trips (not too far, maybe an hour away at most), are Chartres, Versailles, Vaux la Vicomte, Fontainbleau, Giverny, Reims.......Take your pick.
Montmartre accomodations to me are a bit of a pain. Most of the other main sites wouldn't be walking distance from there, for me. And it is uphill, so not a fun walk to return. The metro stops might require a lot of steps to exit there. (But I am 80 years old, so I don't relish lots of steps.) Do visit Montmartre to see the view of Paris from there, and to admire the beautiful mosaics in the Sacre Coeur Basilica. And of course, the Moulin Rouge. But not my first choice for where to stay.
I have given you (probably too many) ideas. Best to check a guidebook (Rick Steves one on Paris is fine) and peruse your Paris options. Have fun on your trip!

It sounds like this might be a first trip to Paris and if that is the case, I would suggest not staying in Montmartre. It will be close to the Moulin Rouge and, of course, Sacre Coeur, but I think it is a bit far away from the most typically visited tourist areas. Have you considered staying in someplace in the first 9 arrondissements such as the Latin Quarter, Le Marais, the Haut Marais, or Saint Germain? Staying in Montmartre is not a deal breaker and I have stayed there and enjoyed it but that was also after I had been to Paris about 10 times and I have a friend who stay only there so ultimately if you like the hills and being a bit of a metro ride from the Louvre, Notre Dame, the Musee d'Orsay, etc., it's a choice.

There are lost of great must do things in Paris but that is a function of what your interests are. If you are interested in large museums, I'd suggest the Museed'Orsay. What about the Eiffel Tower, Arc d'Triomphe, the big department stores, a river cruise, visitng the many churches? The list is almost endless. Please give details of what interests you. I mean are you interested in seeing the big tourist spots, small museums, neighborhoods, shopping etc?

The D-Day trip is a good one and easily done. I'd plan on at least two full days in the area since you have the time. For our first trip there, I had no interest in going there and went to humor my husband and found the area fascinating. You could also do a trip to the Loire Valley or the Burgundy region -- both are very easily reached from Paris. I can't recommend one area over the other. It all depends on what interests you more. In fact, if a 2-hourish train trip is okay for you, there are a ton of areas that you could visit for two or three days of your nine-day trip.

Well, for myself (and Andrea and Judy, I think) I can easily spend 9 days in Paris! BUT, you might want to get a taste of another area.

You can do day trips or you can do a couple of overnights out of town. IF you decide Normandy is important TO YOU, I'd suggest 2 nights in Bayeux with a tour of the landings areas (if they are of interest) with a guide.

In April, Alsace is very pretty. You might do 2 nights in Colmar which is famous for it's Christmas Markets BUT they also have a Spring market. I was there a few years ago and didn't realize it was a "thing", lol. They use the little chalet stalls they use for the Christmas Market but decorate with bunnies, chicks and eggs. It looks like the market is April 4-27 2025.

https://www.printemps-colmar.com/en/

As far as what to see in Paris, there are hundreds of things to see so do what appeals to you rather than what you think you should do. I'm a Louvre person but this museum is huge and confusing and would be torture if you weren't really interested in the treasures that are housed there. I love the Winged Victory of Samothrace, the Botticelli frescos, the vase that belonged to Alienor d'Aquitaine and the Code of Hammurabi. Others feel they should see the Mona Lisa and get caught up in the scrum in front of her. There are many more museums in Paris where the art might be something that might be more enjoyable to people and it's easy to go to them over the Louvre. For the Louvre you will need to book ahead.

My visits are museum heavy whereas others are not. I try to make it a point to go to some of the smaller museums. My last visit, which was in October, I finally made it to the Museum of Hunting and Nature. It was quite interesting even though the stuffed critter they said was a wolf sadly did not look at all like the wolves I've seen here in the US, lol!!

This is our second trip to Paris but travelling with another couple that has never been there. JHK, you mentioned staying in the Loire Valley or Burgandy as a side trip. We do not plan on renting a car. I'm sure these are accessible by train, but do you recommend a certain area in either of those to stay that are very walkable? We are very interested in some wine tasting or winery tours.

I can't give advise about the Loire Valley without a car but I can say that Burgundy is doable without a car. One benefit of not having a car is that all adults in the group can enjoy wine tasting without having to select a designated driver. There are many private or semiprivate wine tours that include transportation between wineries available in the Burgundy region, including a few that leave from Beaune. I happen to like Dijon for a two-day trip better (more non-wine-related things to do IMO) than Beaune, and there are tours that leave from Dijon as well as cavistes that do tastings in town. I did one here and it was quite good: https://lacaveduchaignot.fr/fr/content/19-visites-de-caves-et-degustations-dijon. I did a private tour years ago in the Burgundy region with a British woman and she was excellent but I think she has stopped doing tours -- I'm sure you could find someone by doing some online searching which is how I found the guide I mentioned. There are also bicycle tours but I have never done one. I will mention that the Burgundy region is relatively expensive and the tours and tastings can be pricey.

I just remembered that the place I linked to above is just a 2-minute walk from another place called Aux Vieux Millésime that I think does elaborate tastings. We did not go there but a person we lives in Paris mentioned them. And my husband just reminded me that his team "privatised" La Source de Vins in Dijon, which is another place that does tastings, for a team event so that could be a place for you to research. I know you do not need a car because the team took the train from Paris walked to the tasting and took the train back on a Saturday during a 5-day business trip to Paris.

We stay for a month or more in Paris a couple of times a year and often do side trips. A two night side trip to Bayeux for the beaches is very doable and if you book a tour like Overlord for the full day, no car is needed.

We did one night in Chartres last spring and it was terrific. We wanted to see the illuminations and the last train to Paris was too early to do that in a day trip. We loved it. And we ate at a wonderful restaurant that first night down on the stream below the Cathedral. https://restaurant-moulin-ponceau.fr/fr/

Lyon would work although 3 nights probably better than two and you don't really have time. I would with your limited time in Paris focus on one or two night stays.

Alternatively, there are a couple of dozen great day trips from Paris that don't require an overnight: Versailles, Giverny, Chantilly, Fountainbleau, Moret sur Loing, Crecy la Chapelle, Maintenon, Sceux, Rouen, Reims and the Champagne houses. And many more. I'd be inclined to do that with a short trip.