N-extended super-Liouville theories (for arbitrary N) are obtained from the Wess-Zumino-Novikov-Witten (WZNW) reduction based on the Lie supergroup OSP ( N|2). A gauged WZNW theory is proposed which peovides a lagrangian realization of the reduction, and the path integral equivalence of the constrained WZNW to the super-Liouville is also established.