Thomas Henry Thomas (31 March 1839 – 9 July 1915) was a Welsh artist particularly active in Cardiff. He was also interested in botany, geology, history, and archaeology which were often the subjects of his art works. He was a Fellow of the Royal Cambrian Academy of Art which was established in 1881. He was a leading force behind the founding of the National Museum of Wales and in the use of the red dragon symbolizing Wales.
Thomas was born on 31 March 1839 in Pontypool, where his father was president of the Baptist College, though his parents were from Cardiff. He studied at Bristol School of Art, Carey's Art School, London, then the Royal Academy Schools, before travelling to Paris and Rome. He returned to London in 1861 to work as a painter and illustrator.
In 1866 Thomas returned to settle in Cardiff (Thomas's father had retired there). He inherited his father's house on The Walk in 1880 and this became a place for intellectual discussion in the town. He became very active in the Cardiff Naturalists Society (being president for a while), the Cambrian Academy of Art and the Welsh National Eisteddfod.
He died on 5 July 1915.