The present invention generally relates to waste containers and, more particularly, relates to a locking device for waste containers. The locking device is gravity actuated to an opened position on tilting of the container for dumping. The locking device allows the lid of the container, when the container is in an upright position, to be locked to prevent unauthorized access to the container. When the container is tilted from the upright position, e.g. to empty the contents of the container, the locking device is gravity actuated to allow the lid to open.