During recent fieldwork in Svalbard, a well preserved subfossil left mandible of a polar bear (Ursus maritimus Phipps, 1774) was discovered. A 14C age determination shows that it is older than 45 Ky (kilo-years), and an age determination with infrared-stimulated luminescence—together with the stratigraphic position of the bone—suggests that it is of Eemian–Early Weichselian age: 130–110 Ky old. This makes the find the oldest remains of a polar bear ever discovered. Morphological analyses of the mandible suggest that it comes from a fully grown male that was similar in size to extant male polar bears. The comparative study of other available subfossil polar bear remains did not reveal any significant change in size of polar bears during the Late Quaternary.