A novel inbred maize line designated PHD90 and seed, plants and plant parts thereof. Methods for producing a maize plant that comprise crossing inbred maize line PHD90 with another maize plant. Methods for producing a maize plant containing in its genetic material one or more traits introgressed into PHD90 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 PHD90 or an introgressed trait conversion of PHD90 with another maize line. Inbred maize lines derived from inbred maize line PHD90, methods for producing other inbred maize lines derived from inbred maize line PHD90 and the inbred maize lines and their parts derived by the use of those methods.