A wheat variety designated XW03U, the plants and seeds of wheat variety XW03U, methods for producing a wheat plant produced by crossing the variety XW03U with another wheat plant, and hybrid wheat seeds and plants produced by crossing the variety XW03U with another wheat line or plant, and the creation of variants by mutagenesis or transformation of variety XW03U. This invention also relates to methods for producing other wheat varieties or breeding lines derived from wheat variety XW03U and to wheat varieties or breeding lines produced by those methods.