Yax Nuun Ahiin I was a son of
Spearthrower Owl, a lord of
Teotihuacan (probably that city's king) in central Mexico. The installation of a Teotihuacano noble on the throne of Tikal marks a high point of Teotihuacan influence in the central Maya lowlands. Yax Nuun Ahiin I may have been a child or youth at the time of his coronation, and the early years of his reign seem to have been dominated by one of his father's generals,
Sihyaj K'ahk', in a sort of regency. Sihyaj K'ahk' is recorded as having entered Tikal on 15 May 378, the same date as the death of the previous ruler,
Chak Tok Ich'aak I; it appears that this event may have been a conquest in which Yax Nuun Ahiin I was installed by force. Two monuments at Tikal, Stela 4 and Stela 18, are associated with Yax Nuun Ahiin I. Both stelae depict him in Mexican rather than Mayan attire, demonstrating his Teotihuacano origins. He is also depicted on Stela 31, erected by his son
Sihyaj Chan K'awiil II, as a Teotihuacano warrior with a plated helmet, spearthrower, and square shield decorated with the face of Central Mexican deities. His wife's titles indicate that she may have been a Mayan woman, presumably chosen to integrate his bloodline with the local elites. It is unclear when Yax Nuun Ahiin I died. Stela 31's text indicates that his burial occurred in 404, though the text from another sculpture known as the Hombre de Tikal suggests that he may have still been alive in November 406. On the other hand, the
K'atun ceremony of May 406, which would ordinarily be presided over by the ruler, is recorded as having been presided over by an otherwise unknown individual called Sihyaj Chan K'inich. This suggests that there may have been an
interregnum, possibly with Sihyaj Chan K'inich governing temporarily as a regent, before Sihyaj Chan K'awiil II was enthroned in November 411. ==Tomb==