Lieutenant-Colonel Thomas Vesey, 3rd Viscount de Vesci (21 September 1803 – 23 December 1875), was an Irish peer and Conservative politician.
de Vesci was the son of John Vesey, 2nd Viscount de Vesci, and Frances Letitia, daughter of William Brownlow.
de Vesci sat as Member of Parliament for the Queen's County between 1835 and 1837 and 1841 and 1852. In 1857 he was elected an Irish Representative Peer and entered the House of Lords.
Lord de Vesci married Lady Emma, daughter of George Herbert, 11th Earl of Pembroke, in 1839. He died in December 1875, aged 72, and was succeeded by his son, John. His daughter, Beatrice Charlotte Elizabeth, married Lord Richard Grosvenor, a brother of the 1st Duke of Westminster.
Lady de Vesci founded the Abbeyleix Baby Linen Society, a co-operative enabling women access to affordable baby clothing. She died in October 1884, aged 65.