We have created and characterized a transmissive diffraction grating that disperses 8 keV x rays. The grating has a period of 7077±70 A˚ and consists of opaque zones of Ta separated by transparent zones of Al. It was fabricated by sputtering alternating layers of Al and Ta onto a glass optical flat and then slicing the coating into a 17‐&mgr;m‐thick slab. We tested the performance of the grating against a theoretical prediction by exposing the grating to 8 keV radiation from a Cu x‐ray source and observing the interference pattern.