John Thomas Browne, 4th Marquess of Sligo (10 September 1824 – 30 December 1903), styled Lord John Browne until 1868, was an Irish politician and naval commander.

Browne served as a Liberal Member of Parliament for Mayo in Ireland from 1857 to 1868. He had previously served as an officer of the Royal Navy.

In 1896, Browne became Marquess of Sligo on the death of his elder brother, the 3rd Marquess, also inheriting some 114,900 acres (465 km²) of land and the family seat at Westport House, Westport, County Mayo.^[1] He died unmarried and was succeeded by his brother, Henry.