A novel maize variety designated PHHRJ and seed, plants and plant parts thereof. Methods for producing a maize plant that comprise crossing maize variety PHHRJ with another maize plant. Methods for producing a maize plant containing in its genetic material one or more traits introgressed into PHHRJ through backcross conversion and/or transformation, and to the maize seed, plant and plant part produced thereby. Hybrid maize seed, plant or plant part produced by crossing the variety PHHRJ or a trait conversion of PHHRJ with another maize variety. Inbred maize varieties derived from maize variety PHHRJ, methods for producing other inbred maize varieties derived from maize variety PHHRJ and the inbred maize varieties and their parts derived by the use of those methods.