A ompat, efficient, high‐brightness pulsed plasma x‐ray source has been demonstrated. The source has a conversion efficiency, from electrical input to usable x‐ray energy, of greater than 1%. For example, total radiated yields of 150 joules of neon K‐line radiation have been produced in a single pulse. X‐rays are emitted from a cylindrical volume approximately 1 mm in diameter and 10 mm long. Various wavelengths can be obtained by the choice of appropriate plasma materials. This x‐ray source compares favorably to synchrotron radiators in intensity, and most users of synchrotrons will find this source attractive.