Archaeological excavation of a natural boulder chamber on the upper slopes of Bengorm Mountain, County Mayo, in the northwest of Ireland revealed evidence for complex Neolithic funerary rituals spanning several centuries. With virtually no subsequent evidence of animal or human disturbance, the site presents an exceptional insight into well-preserved engagements with the dead at a remote mountain location where themes of secrecy, continuity and ritual grammar are highlighted. The chamber was used for processing individuals of all ages but there is a tentative suggestion that the space was reserved predominantly for males. Ancient genomic analysis reveals kinship between at least two adult males, both of whom were almost certainly intermediate to dark skinned, with brown eyes and dark brown or black hair. Both individuals were also lactose intolerant.