The new properties of third-generation synchrotron radiation beams call for corresponding progress in instrumentation technology. This is particularly true for hard x-ray mirrors, for which new technologies have been implemented to meet outstanding requirements. The transfer of experience from other fields such as high-energy lasers and astronomy has been of major importance in the realization of new designs. The European Synchrotron Radiation Facility, the first third-generation hard x-ray source in Europe, has stimulated R&D programs of four European companies in the field of hard x-ray mirrors. This paper presents the major achievements of these companies.