In Celtic mythology, the Fianna were Irish warriors who served the High King of Ireland. In the AD 3rd century, their adventures were recorded in the Fenian Cycle. Their last leader was Finn mac Cumhail.

Member included:

• Finn mac Cumhail: last leader of the Fianna
• Cailte mac Ronan
• Cumhail
• Conan mac Moirna
• Conan Maol
• Diarmait, Son of Don: was a warrior of the Fianna before he ran off with Finn's bride Grainne and was finally killed by a giant boar on the heath of Benn Gulbain. Foster son of Oengus.
• Lughaid Stronghand: sorcerous warrior, nephew of Finn mac Cumhail, one of the four who could have untied the knots Diarmait bound the seakings with, but refused to do so. Lover of Aife, daughter of Manannan
• Oisin, son of Finn mac Cumhail: (Mc Phersons's Ossian)
• Osgur, Son of Oisin

Alternatives: Fenians, Fianna Éireann

Fianna can also refer to the Fianna Eireann

Fianna is used in the name of one of the major Irish political parties, Fianna Fáil.

Fianna is used in the name of a tribe in the game Werewolf: The Apocalypse; see Fianna (Werewolf the Apocalypse).