What is the traditional New Year's Eve dinner called in France?

The traditional New Year's Eve dinner in France is called a réveillon.

A réveillon is a long, festive meal associated especially with Christmas Eve and New Year's Eve. The word comes from the French réveil, meaning “awakening,” reflecting the idea of staying awake late into the night. A New Year's réveillon may include several courses, champagne, seafood, foie gras, desserts, and other special foods, although menus vary by household and region.

The term is not limited to New Year's Eve. In France, réveillon de Noël refers to the Christmas Eve meal, while réveillon de la Saint-Sylvestre refers to the New Year's Eve celebration. Context usually identifies which holiday is meant.

A réveillon is a meal or celebratory gathering, not the name of a particular dish. That distinction prevents confusion with bûche de Noël, a Christmas log-shaped dessert, or galette des rois, traditionally associated with Epiphany.