Abstract: In order to secure a door in a locked (or locked open) position without a key, such as to resist a forced entry through the door, a removable, remotely-controlled door locking apparatus is provided, which includes a rear plate for attachment against a surface of a door, a cover for enclosing components on the rear plate, and a telescoping arm assembly connected to the rear plate and extendible so that the other end attaches to a door knob. A DC-powered linear actuator connected to the rear plate and at least one electronics module configured to communicate wirelessly is within the cover. A foot of the actuator is configured to be extended in a lock state against a floor surface to secure the door or retracted in an unlock state, based on a wireless signal received from a remote smart device to control the actuator.