The burial rites of the Yotvingians, a people who inhabited the Suwalki region of north-eastern Poland, were until recently almost completely unknown to archaeologists. For a long time, it was considered that the funeral rites of this people could not be identified archaeologically, and while finds such as settlement complexes have been excavated, related necropolises were not found. This changed with the identification of the Mosiezysko burial ground in the Szurpily settlement complex, dated to the twelfth and thirteenth centuries AD, which is the first sepulchral site of the early medieval Yotvingians to have been discovered and surveyed using state-of-the-art archaeological methods. The results from these excavations are presented for the first time in this monograph. The excavations at the site yielded traces of collective cremation burials discovered scattered on the surface of the site, accompanied by stone structures. The equipment of the deceased, intentionally destroyed and burnt, included numerous fragments of ornaments, parts of costume and tools, as well as sporadically occurring weapons and horse riding gear. In addition to finds of artefacts characteristic of the early medieval Suwa?ki region, it was also possible to distinguish interregional varieties akin to finds from Sambia, Curonia, and other lands inhabited by the Balts. The results of this ground-breaking find, documented here, have now made it possible to expand research into the Yotvingians, and to identify similar sites.