Wing Chun is a form of Chinese martial arts, which are sometimes called "Kung Fu", though that term loosely means "skill" and can refer to anything from fighting to painting to tailoring. In turn, the expression "martial art" means any codified fighting system. So Wing Chun is, by definition, a martial art, and can very well be classified as a type of "kung fu". Other martial arts include things like Judo, karate, Taekwondo, and kickboxing.