A novel maize variety designated X15K726 and seed, plants and plant parts thereof are produced by crossing inbred maize varieties. Methods for producing a maize plant by crossing hybrid maize variety X15K726 with another maize plant are disclosed. Methods for producing a maize plant containing in its genetic material one or more traits introgressed into X15K726 through backcross conversion and/or transformation, and to the maize seed, plant and plant part produced thereby. This invention relates to the maize variety X15K726, the seed, the plant produced from the seed, and variants, mutants, and minor modifications of maize variety X15K726. This invention further relates to methods for producing maize varieties derived from maize variety X15K726.