Examples of a rail-mounted robotic inventory system are provided. The system includes a rail-mounted robot having an electronic tag reader configured to receive electronic tag data from electronic tags associated with inventory items. The system can include a navigation module configured to direct the rail-mounted robot along a rail through an inventory area, detect obstacles, and determine a position of the rail-mounted robot within the inventory area. The system can include an inventory identification module configured to receive the electronic tag data from the rail-mounted robot and identify and/or locate the inventory items in the inventory area based at least partly on the electronic tag data.