Tír na hÓige (Land of Youth) is perhaps the most beloved name in the Irish otherworld geography, associated above all with the story of the poet-warrior Oisín who travels there with the goddess Niamh and returns to find centuries have passed in Ireland. The tragedy of Oisín's return — his world gone, his companions dead, his body crumbling the moment he touches Irish soil — became one of the great archetypes of Irish poetry, used by Yeats in his early long poem The Wanderings of Oisin. Tír na hÓige embodies the impossible desire to escape mortality, and its failure in the Oisín story gives the image its elegiac power.

Tír na nÓg (Land of Youth) is a supernatural paradise of eternal youth and beauty in Irish mythology. It is a place of escape from aging and death, often reached by sea. In poetry, Tír na nÓg represents the ultimate desire for permanence and perfection. It contrasts with the transience of mortal life, offering a vision of ideal existence. However, returning from Tír na nÓg often results in rapid aging, highlighting the cost of such escapism. It is a key concept for understanding the otherworldly aspirations in Irish literature.