Fíanaíocht encompasses both the prose tales of the Fianna and the extensive lyric verse associated with the cycle, including the laoithe (lays) attributed to Oisín and Caílte. The tradition is notable for its intense engagement with the natural world — mountains, forests, rivers, and seasons — described in poetry of great sensory richness. The elegiac tone of much Fenian verse, reflecting on the passing of the heroic age, gave it particular appeal for modern poets and for the Romantic tradition more broadly. James Macpherson's controversial Ossian poems, however misrepresenting the originals, introduced fíanaíocht materials to an international audience and transformed European Romanticism.

Fíanaíocht is the body of lore concerning the Fianna, warrior bands led by Fionn Mac Cumhaill. It emphasizes values of loyalty, hunting, and living outside settled society. In poetry, fíanaíocht represents a romanticized ideal of freedom and heroic camaraderie. It contrasts with the courtly world of the Ulster Cycle, offering a different model of masculinity and social organization. Poets use fíanaíocht imagery to evoke nostalgia for a wilder, more autonomous past. It is a rich source of adventure narratives and moral tales.