Yes, Opéra De Nuit is definitely a goth band because most of their albums belong to the Coldwave genre, which is a core subgenre of goth music. Albums like Opéra De Nuit, Amour Noir, and Sourire De L'ombre are examples of their goth sound.
Opéra De Nuit is located in France, active in 1982 — 1989. You can find more information about Opéra De Nuit on their GothDB band page.