Sebastian Ulicke Browne, 12th Marquess of Sligo (born 27 May 1964), is a peer in the Peerage of Ireland.
The son of Captain Lord Ulick Browne (1915–1979) and his second wife Fiona Glenn, he was educated at Rugby School. He married Christina Maria Suaznabar, of Bolivia, in 1984, by whom he has two children:Lady Camilla Browne (b. 1986)
Christopher Ulick Browne, Earl of Altamont (b. 14 November 1988)
The couple divorced in 1992.
He emigrated to Australia in 1997, where he is a residential real estate agent. He succeeded his first cousin as 12th Marquess of Sligo in 2014, although the 11th Marquess had dissolved the entail on the family estate of Westport House and left it to his daughters. On 22 January 2016, Sligo married Claire Suzanne van Middelkoop in Wollongong.