The SNCF (Société Nationale des Chemins de Fer) operates long-distance trains (Inoui, Ouigo & Train de nuit) and regional express trains (TER/ZOU!).
SNCF provides 11 regular connections from abroad and 20 daily connections from the most important French cities. The TGV (High Speed Train) connects Paris to Nice in 5h30.
SNCF Voyageurs SUD AZUR also provides 110 daily trains on the Côte d'Azur around 51 stations.
https://www.ter.sncf.com/sud-provence-alpes-cote-d-azur.