Getting a Bicycle for a Month in France?

Try going to a local bike store, or at ask your hotel for leads. If you're in an Airbnb or similar, email your host before arriving. Maybe they have suggestions.

I suggest you contact the Colmar bike shops and see what they can do for you. Some of them are listed here:

https://www.tourisme-colmar.com/en/practical/travel-and-mobility/colmar-by-bike

And Google will help you find others.

I'd email some local bike shops and see what is possible. Maybe they would buy a purchase back from you at the end of the month (for substantially less than you paid, I would think, but that is fair, or at least better than otherwise).

You can buy an inexpensive bike for a month and then donate it to Erasmus or one of the other big French charities?
Leboncoin is one of the larger craigslist-type sale websites in France.
Go to leboncoin.fr, click on "Rechercer" at the top, "x" out the current location to the right and enter "Colmar". Use the "Categories" drop down menu, look under the "loisirs" section and click on "velos". Then click the blue field marked "Rechercher".
Maybe you'll find just what you're looking for?? I just ran that search and there are a ton of bikes of all kinds for sale in the Colmar area. Plenty under 100 euros.

Many supermarkets sell bikes in the summer at reasonable prices, unless you want a Tour de France quality machine!

Ozzies/Kiwis often buy a car for their vacation then sell it when they leave. It seems to me a used bike purchase is a great idea. It's not unusual for bike shops to sell used bikes (if you can't find something for sale elsewhere).

You can either sell them at the end of your trip or donate them.

Thank you all for these good ideas!

We are cycling in France for the month of June and are renting bikes from French Bike Rentals which will deliver and pick up bikes anywhere in France, Spain or Italy. There are savings for rentals greater than 7 days and they have a terrific range of really good bikes. Cycling is the purpose of our holiday so getting really good bikes was important to us but this probably isn't what you are looking for. But perhaps one of the cycle rental shops might have bikes they are selling at a discount. As we had researched a lot of bike rental options we ended up on quite a few email lists and several shops sent us emails with offers to buy last year's rental bikes at a discount. The delivery charge might not be worth it but thought it was worth a mention on the off-chance.

Nice, thanks!

Contact and negotiate for 2 velos for a month at A COLMAR, TOUS A VELO

This is interesting. I see they do very cheap monthly bike rentals for employees and students. You think there's a good chance we could get a cheap monthly rental (perhaps a bit more expensive) even though we're not either?

Sorry, but a rental bike is not going to win the Tour de France under any circumstance.

LOL... thankfully we're not trying to do anything remotely like that! Just a bit of getting around the nearby villages.