A novel inbred maize line designated PHA9G and seed, plants and plant parts thereof. Methods for producing a maize plant that comprise crossing inbred maize line PHA9G with another maize plant. Methods for producing a maize plant containing in its genetic material one or more traits introgressed into PHA9G 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 inbred line PHA9G or an introgressed trait conversion of PHA9G with another maize line. Inbred maize lines derived from inbred maize line PHA9G, methods for producing other inbred maize lines derived from inbred maize line PHA9G and the inbred maize lines and their parts derived by the use of those methods.