Travel from Rome to Nice, by car

Renting a car in one country and returning it a different country usually incurs a large surcharge. Visiting France and returning the car at a different location in Italy is usually no problem.
Don't forget to allow for Autostrada tolls in Italy and Autoroute tolls in France.

For your planning use https://www.viamichelin.com/ This shows routes, distances, times and costs including tolls. Add 25% to 50% to all times, the ones quoted assume you don't stop for anything.

If your licence is from outside the EU, you will need an International Driving Permit (IDP) as well as your licence to drive in either country. Despite what many posts say ("the rental company never asked for it, it was not needed"), it is not a requirement of the rental company, it is a legal requirement to drive any car, rented borrowed or owned by you.

If you can drop the car at Ventimiglia (border city), there should be no iner-country dropoff charge. Then take the train to Nice. If you need to rent a car in France, you can pick one up in Nice.

Some years ago, we did as Zoe suggested. However, at that time, the closest place to the border where we could drop a car was San Remo. Maybe now you can do it at Ventimiglia. It will work just fine in either case. There are car rental offices very close to the train station in Nice, if you need another car.

Sue,

As mentioned in the first reply, renting in one country and dropping in another often comes with a hefty surcharge.

For driving in both countries, it's important to note that each driver listed on the rental form must have the compulsory International Driver's Permit, which is used in conjunction with your home D.L. (so you must carry both). In France you can also use a certified translation in French of the terms of your D.L. I.D.P.'s are valid for one year, and easily obtained at any CAA/AAA office (two Passport-sized photos required, which may be provided by the issuing office).

You may also want to have a look at some of the posts on the forum concerning the dreaded Zona Traffico Limitato (limited traffic) areas that are becoming increasingly prevalent in many Italian towns & cities (especially Florence!). Some of these are enforced by automated cameras and some by local police. Each pass through one of the automated Cameras will result in a €100+ ticket and visitors often don’t know of these violations until several months after they’ve returned home.

I think there is an AVIS franchise in San Remo.
All others are available in Savona.
No major rental companies in Ventimiglia that I could find.

Are you thinking of driving straight there, or over several days with stops along the way? If straight, then I'd fly EasyJet, instead.

Your other, concurrent thread is about Rome-Sorrento. If you give us a fuller idea of your trip plan, some responders might have an insight beyond your specific questions. Are you flying into Rome, then south heading to Sorrento, then heading north? Do you need to go through Rome a second time? EasyJet also flies from Naples to Nice.

Great thanks!
We are flying into Rome with our 3 adult kids. Staying 3 days in Rome, going Sorrento, for 2 days and 3 in Positano. Then we take our kids to the Rome airport to go home. My husband and I are there 4 more days.
We thought going south France would be fun, but we dont have to. We have been to Venice, Cinque
Terre, Florence, Tuscany Milan. Open to anything fantastic. It doesnt have to be Nice. Just want to experience something like Provence. But thats to far. Or we can stay in Italy or Lake Como. That you can't always do with kids. Also flying out of Milan.
Thanks for input.

Consider visiting Sardinia. From FCO it's a one hour flight to Càgliari. Stay a night in Càgliari and then drive up the west coast through Burimini (to visit Su Nuraxi) to spend a night in Oristano. Then a night in Alghero visiting the surrounding countryside. Depending on time, you might want to cross over to Olbia on the east side of the island. Many inexpensive flights from both cites to Milan. I found Sardinia to be a beautiful island with phenomenal beachs, unique gastronomy and great people. As Sicily is different from the mainland, Sardinia is as well and doesn't disappoint.