Abstract: A needle shield assembly having a single-use lock includes a needle cannula having a proximal end connected to a hub. A collar is connected to the hub and an elongate rigid needle cover removably engages the hub and covers the needle cannula. An elongate needle shield is hingedly connected to the collar. The needle shield has two side walls defining a longitudinal opening. The needle shield is capable of pivoting from an open position where the needle cannula is exposed, to a closed needle protecting position where the needle cannula is within the longitudinal opening of the needle shield. Structure is provided for preventing the needle shield from being pivoted into the closed needle protecting position until the needle cover is removed. Structure is also provided for automatically locking the needle shield in the closed needle protecting position when the needle shield is pivoted into the closed position.