Cormac Breathnach (died 29 May 1956) was an Irish national school teacher and politician.
Breathnach served as Lord Mayor of Dublin from 1949–1950 and had been involved in the National Labour Party before being convinced to switch his political allegiances by Éamon de Valera, the founder of Fianna Fáil.
He was first elected to Dáil Éireann at the 1932 general election. From 1932 to 1937 he served as a Fianna Fáil Teachta Dála for the Dublin North constituency. In 1937, he moved to the Dublin North West constituency and served there until 1954. He did not contest the 1954 general election.