French language dictionaries can be found in Hatcher Reference Room and 4th floor South Stacks in the call number range PC2001 - PC3761.
These dictionaries are available online:
Oxford Reference Online
Includes The Concise Oxford-Hachette French-English Dictionary as well as The Oxford Business French Dictionary.
Le Grand Ricci Online
A comprehensive Chinese-French dictionary
Historical French language dictionaries
Check out this Hathi Trust Digital Library collection, where you can search for a word of interest across multiple dictionaries.
ARTFL's Dictionnaires d'autrefois
Includes Dictionnaire de l'Académie Française, Littré’s Dictionnaire de la langue française, as well as Jean Nicot’s Le Thresor de la langue françoyse, tant ancienne que moderne and Jean-François Féraud’s Dictionaire critique de la langue française.
Trésor de la langue française (in print)
Not the dictionary one might consult for a quick definition, but if you wish to understand a word in all in meanings and ramifications, its orthographic and etymological history, then this is the dictionary for you. Though limited to the French of the 19th and 20th centuries, this is still one of the most comprehensive and exhaustive of all dictionaries.
Hatcher Graduate Library PC 2650 .I32