Thomas McCabe (1739 - 1820) was a founding member of the Society of the United Irishmen, a revolutionary organisation in late 18th century Ireland.
A native of Belfast and member of the First Presbyterian Church, McCabe owned a cotton mill and a clock making shop in the city. Along with other future United men, such as Henry Haslett and William Tennant, he was a Freemason and a member of Lodge 684. He married Jean Woolsey, daughter of John Woolsey, a merchant of Portadown and together they had four children. Their third child was William Putnam McCabe,a fellow Freemason, who would also join the United Irishmen, and was important in organising Ulster prior to the 1798 Rebellion. Jean died in 1790.
Thomas was one of the founding members of the Belfast Charitable Society, Clifton House, Belfast in 1774. In the 1770s, McCabe and John McCracken (father of United Irishman Henry Joy McCracken) installed machinery in the Clifton House, known then as Belfast Poor House, enabling it to become the first cotton spinning mill in the town. An important member of Belfast's mercantile and industrial middle class, he donated £100 to the building of a new White Linen Hall in 1782, to act as a centre for the bustling linen industry in the city. Another important benefactor to the building of the hall, was fellow future United Irishman, Gilbert McIlveen.
Prior to the founding of the United Irishmen, McCabe was heavily involved in Belfast's liberal and radical community, being a leading figure in the city's anti-slavery circle. He clashed routinely with the plans of Waddell Cunningham and others to form a Belfast-based slave trading company of which he wrote, ‘May God eternally damn the soul of the man who subscribes the first guinea’. In 1786, he prevented a slave-owning shipping company from setting up business in Belfast. These exploits led Theobald Wolfe Tone to style him as the 'Irish Slave'.