Fennagh, Fenagh or Feenagh may refer to:
Places Feenagh, County Clare, a civil parish in County Clare, Ireland Feenagh, County Limerick, Ireland Fenagh, County Leitrim, a civil parish in County Leitrim, Ireland Fennagh, County Carlow, Ireland Fenagh (crater), a crater on Mars
Other uses Book of Fenagh, a manuscript of prose and poetry written in Classical Irish at Fenagh, County Leitrim