Thomas St George McCarthy (1862–1943) was an Ireland rugby union international and founder member of the Gaelic Athletic Association, being present at Hayes Hotel, Thurles, County Tipperary, Ireland at the Association's inaugural meeting on 1 November 1884.
At the foundation of the GAA, McCarthy was a District Inspector of the Royal Irish Constabulary based at Templemore, County Tipperary.
Later in 1882, he was a member of the Dublin University team which won the Leinster Senior Cup, the inaugural year of this competition.
He was a regular attender at matches in Croke Park to where he travelled from his home at Oakley Road in the Dublin suburb of Ranelagh.
He died in 1943 and was buried without fanfare in an unmarked grave in Deansgrange Cemetery, Dublin, though there is a family plot in the old graveyard at Bansha village, where his sister, Kathleen McCarthy, is interred.