Robert Stewart, 1st Marquess of Londonderry (September 27, 1739) - (April 6, 1821) was an Irish politician and landowner, and father of the famous politician Robert Stewart, Viscount Castlereagh.

Born in 1739, the grandson of a very rich Governor of Bombay, Stewart was elected to the Irish House of Commons in 1771 as member for County Down, becoming an Irish Privy Counsellor eleven years later. In 1789 he was created Baron Londonderry in the Peerage of Ireland, and in 1795 became Viscount Castlereagh. The following year he was promoted as Earl of Londonderry, and finally in 1816 was created Marquess of Londonderry, again in the Peerage of Ireland. From 1801 until his death he was also an Irish representative peer. He died at his home of Mount Stewart, County Down, and was buried at nearby Newtownards.

Reference

• LONDONDERRY, EARLS AND MARQUESSES OF, 1911 Encyclopedia Britannica; [1] (http://22.1911encyclopedia.org/L/LO/LONDONDERRY_ROBERT_STEWART_2ND_MARQUESS_OF.htm)