Táin Bó Cúailnge
His sister Cecile O'Rahilly was also a Celtic scholar, and published editions of both recensions of the "Táin Bó Cúailnge" and worked with her brother in the School of Celtic Studies at the Dublin Institute for Advanced Studies. Their brother Alfred O'Rahilly, himself a noted academic, was President of University College Cork and Teachta Dála (TD) for Cork City.