The fairy queen in Irish mythology who lured the hero Oisín to Tír na nÓg was Niamh.
Usually called Niamh Chinn-Óir, meaning “Niamh of the Golden Hair” or “Golden-headed Niamh,” she is an otherworldly woman in the Fianna Cycle. She falls in love with Oisín, the warrior-poet and son of Fionn mac Cumhaill, then invites him to leave Ireland and live with her in Tír na nÓg, the Land of Youth.
The enchanted realm is associated with beauty, abundance, health and freedom from ordinary ageing. In the best-known version, Oisín spends more than 300 years there, although the passage of time feels much shorter. When he returns to Ireland, Niamh warns him not to touch the ground. He eventually falls from his horse, ages instantly and cannot return to her.
Niamh is sometimes described as a princess rather than a queen, depending on the retelling. That variation does not change her identity in this story. Étain, Brigid and Áine are also important Irish mythological figures, but none is the woman who takes Oisín to Tír na nÓg.