Thomas O'Mahony (died 20 July 1924) was an Irish Cumann na nGaedheal politician who sat as a Teachta Dála (TD) in Dáil Éireann in the 1920s. At the 1923 general election, he was elected for the Cork East constituency to the 4th Dáil. He died less than a year later, on 20 July 1924. The by-election for his Dáil seat was held on 18 November 1924, and won by the Cumann na nGaedheal candidate Michael K. Noonan.