Thomas McCarthy Fennell (December 22 1841–February 23 1914) was a Fenian political prisoner transported as a convict to Western Australia.

Born in County Clare, Ireland in 1841, Fennell was just four years old when the Irish Potato Famine struck. Nonetheless he received a good education, attending either a Catholic school or a national school, and he learned to speak Gaelic at home.

In 1863, Fennell became one of the first Fenians recruited from County Clare; he then helped recruit and organise a group of men in preparation for the Fenian Rising. On 5 March 1867, six Fenians men entered the Kilbaha coastguard station, and demanded the station's arms "in the name of the Irish Republic". A scuffle ensued, and Fennell was shot through the hip and testicle. The group retreated, and Fennell was treated for his injuries. He was arrested three days later. Tried for treason in the Clare Assizes, on 15 July 1867 he was found guilty and sentenced to ten years' penal labour. Initially he was lodged at Mountjoy Prison, a clearinghouse for political prisoners; later he was transferred to Portland prison. In October 1867, he was put on board the Hougoumont, a convict ship bound for Western Australia. The Hougoumont departed Portland on October 12 1867 and arrived at Fremantle, Western Australia on January 9 1868.