Best definition
A person who is a fan of the classical composer Richard Wagner (like you say Beatlemaniac for someone who is

a fanatic of The Beatles). May also be wagnerite.

Person: I am a Wagnerian because I like Ride of the Valkyries because it was used in Apocalypse Now by the director who made the Godfather-

Other person: Um… any other pieces by Wagner?

Person: Uh…