An inbred corn line, designated XHA21BM, the plants and seeds of the inbred corn line XHA21BM, methods for producing a corn plant, either inbred or hybrid, produced by crossing the inbred corn line XHA21BM with itself or with another corn plant, and hybrid corn seeds and plants produced by crossing the inbred line XHA21BM with another corn line or plant and to methods for producing a corn plant containing in its genetic material one or more transgenes and to the transgenic corn plants produced by that method. This invention also relates to inbred corn lines derived from inbred corn line XHA21BM, to methods for producing other inbred corn lines derived from inbred corn line XHA21BM and to the inbred corn lines derived by the use of those methods.