This paper reports the results of an in-depth analysis of the frozen remains of a woolly mammoth (Mammuthus primigenius) named Zhenya, which has been dated to 48,000 cal BP. The carcass, found near the mouth of the Yenisey River in eastern Siberia, was a juvenile male whose ontogenetic age at death was 8–10 AEY. Its reconstructed live height at the shoulders (pSH 227.4 cm) was the equal of some adult female woolly mammoths and extant elephants. The large stature and a flaked off tusk tip that matches breaks on tusks of male African elephants are indirect indications that this mammoth most likely had reached sexual maturity, had been expelled from its maternal herd, and had been in at least one fight with another male. The mammoth’s bones were relatively healthy, although some had minor lesions. Rudimentary upper second molars (M2/m2) were present, but no lower second molars were found in the alveoli, and the left tusk had never developed. Despite the abnormal development of the upper and lower second molars, the cheek teeth which were in wear (Dp4/dp4 and M1/m1) showed normal function without any indications of developmental delay. The completed growth of the light-colored dentin bands on the tusk strongly suggests the Fall of the year was the season of death. This season is also supported by accumulated fat in the upper parts of the torso, indicative of physiological preparation for the winter ahead. The few minor traces of carnivore scavenging, the little disturbed condition of the carcass, and the absence of bone modifications made by human actions, along with the social status of this young male animal, are interpreted here as highly probable evidence that the Zhenya Mammoth died from unrecoverable injuries inflicted during a bull-to-bull fight. The mineralogical analysis of site sediments revealed that the mammoth’s burial in situ took place in the Yenisey River valley seasonally inundated by the river, which together with Fall’s freezing temperatures protected the carcass from scavengers. An analysis of ancient DNA provides strong support for Zhenya’s mitochondrial lineage within the deeply diverging clade III haplogroup B.