Abstract: A locking/unlocking mechanism for a contactless gesture detection system of a device is described herein. The locking/unlocking mechanism can facilitate automatic locking, manual locking, and/or manual unlocking of the contactless gesture detection system. The contactless gesture detection system can implement the locking/unlocking mechanisms described herein to control a contactless gesture-based user interface state of the device. In various implementations, the controlling can include detecting gestures associated with a user in a contactless space associated with the device; detecting a defined gesture sequence over a defined time period from the detected gestures; and transitioning the device to a contactless gesture-based user interface locked state or a contactless gesture-based user interface unlocked state based on the defined gesture sequence.