A region monitoring system includes: a first communication control unit that transmits monitoring camera captured-image data to a monitoring server, the monitoring camera captured-image data being captured-image data of a monitoring camera that monitors a region in which a plurality of houses are located; and a camera communication control unit that transmits in-vehicle camera captured-image data to the monitoring server, the in-vehicle camera captured-image data being captured-image data of an in-vehicle camera of a vehicle located in the region.