The present invention relates to bicyclic aryl monobactam compounds of Formula (I), and pharmaceutically acceptable salts thereof, wherein A1, L, M, W, X, Y, Z, RX and Rz are as defined herein. The present invention also relates to compositions which comprise a bicyclic aryl monobactam compound of the invention or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier. The invention further relates to methods for treating a bacterial infection comprising administering to the patient a therapeutically effective amount of a compound of the invention, either alone or in combination with a therapeutically effective amount of one or more beta-lactamase inhibitor compounds.