Paris to Rome by Airlines
Ryan Air, Wizzair and Blue Air fly from Paris Beauvais Tille Airport BVA. You can get a shuttle from Paris to this airport for €13.
EasyJet flies from Orly Airport (ORY) to Rome (Ciampino).
Many of the larger carriers fly to Rome from from Paris Charles de Gaulle (CDG)
Check airfare prices on Expedia
Paris to Rome by Night Train
The night train from Paris to northern Italy is called Artesia. It takes about 14 and a half hours to get from Paris to Rome. It leaves Paris from the Gare de Bercy Train Station. You must reserve your space on the Artesia and pay a supplimental fee. If you have a France-Italy rail pass you will pay less.
Many people like this option, although even with a rail pass it could be more expensive than a budget airline. Passengers cite the scenery in southern France, eating a meal while that scenery is passing by, and having space for the kids to play.
All passengers on the Artesia sleeper trains from Paris to Italy must reserve a sleeping berth in either a sleeping-car or more economical couchette car (4 or 6 bunk-style beds.) You cannot just book a seat on these trains, although the beds convert to a seat for the morning.
For more information and ticketing on Artesia, see the Rail Europe FAQ on Premier Trains.
For a regular rail pass that covers France and Italy: France-Italy Rail Pass (Buy Direct)
Paris to Rome by Bus
Eurolines runs a bus from Paris to Rome.