For many years the primitive extinct toothed whale genus Patriocetus has been known only from the holotype partial skull of P. ehrlichi (van Beneden, 1865), and a more nearly complete paratype skull, both from uppermost Oligocene sands near Linz, Austria, in the western Paratethys region. A virtually complete skull found in Late Oligocene beds on the Mangyshlak Peninsula of the Republic of Kazakhstan in the 1960s is the first specimen of Patriocetus known from the eastern Paratethys region, extending the range of this genus approximately 4,000 km eastward from the type locality of the genus at Linz. Herein named Patriocetus kazakhstanicus, this new species of Patriocetus differs from P. ehrlichi in size, morphology, and dental count. Direct comparison of the holotype skull of P. kazakhstanicus to that of P. ehrlichi has provided a more accurate definition of the arrangement of the bones in the skull roof of P. ehrlichi, long a source of uncertainty because sediment cemented to the surface of both the holotype and the paratype of the latter species partially obscures the sutures, making it difficult to determine the boundaries of the frontals, parietals, and supraoccipital. The skull of P. kazakhstanicus also shares well-defined generic characters with the partial skull of an undescribed species of Patriocetus from Germany (Rothausen and Sanders, in preparation), for which there are casts of the complete skull. The rostra of those two specimens are more nearly complete than those of the holotype and the paratype of P. ehrlichi, each of which is missing the anterior end of the rostrum. All four specimens share similarities in dentition and rostral characters that now confirm Rothausen's (1968) conclusions that members of the genus Patriocetus were longirostrine forms.