Fiach is an Irish male given name. It may refer to:
- Saint Fiacc, fifth-century bishop of Sletty in Ireland
- Fiach McHugh O'Byrne (1534–1597) Irish chief
- Fiach Mac Conghail (born 1964) Irish theatre director and Senator
- Fiach Moriarty, Irish singer-songwriter
See also
edit- Tomás Ó Fiaich, Irish Catholic primate and cardinal