Baron Rossmore, of Monaghan in the County of Monaghan, is a title in the Peerage of Ireland. It was created in 1796 for the soldier Robert Cuninghame, with remainder to his wife Elizabeth's nephews Henry Alexander Jones (the son of Theophilus Jones and Anne Murray, eldest sister of Elizabeth; Henry Alexander Jones died childless before his uncle Lord Rossmore) and Warner William Westenra and Henry Westenra, sons of Henry Westenra and Harriet Murray, youngest sister of Elizabeth. Cuninghame was a General in the Army and served as Commander-in-Chief of Ireland. From January to August 1801 he also sat in the House of Lords as an Irish Representative Peer.
Lord Rossmore died childless and was succeeded according to the special remainder by his nephew Warner William Westenra, the second Baron. He represented Monaghan in the British House of Commons and also served as Lord Lieutenant of Monaghan from 1831 to 1842. In 1838 he was created Baron Rossmore, of the County of Monaghan, in the Peerage of the United Kingdom. This gave the barons an automatic seat in the House of Lords. His eldest son, the third Baron, represented Monaghan in Parliament as a Whig and was Lord Lieutenant of Monaghan from 1843 to 1852. His younger son, the fifth Baron (who succeeded his elder unmarried brother), was Lord Lieutenant of Monaghan from 1897 to 1921. As of 2014[update] the titles are held by the latter's grandson, the seventh Baron, who succeeded his father in 1958.
The Westenra family is of Dutch descent. Warner Westenra (died 1676) emigrated to Dublin and became an Irish subject. The seat of the Barons Rossmore was Rossmore Castle, County Monaghan. Warner Westenra, grandfather of the second Baron, represented Maryborough in the Irish Parliament. Henry Westenra, father of the second Baron, represented County Monaghan in the Irish Parliament. The Honourable John Westenra, third son of the second Baron, was Member of Parliament for King's County.
Barons Rossmore (1796)
- Robert Cuninghame, 1st Baron Rossmore (1726–1801)
- Warner William Westenra, 2nd Baron Rossmore (1765–1842)
- Henry Robert Westenra, 3rd Baron Rossmore (1792–1860)
- Henry Cairnes Westenra, 4th Baron Rossmore (1851–1874)
- Derrick Warner William Westenra, 5th Baron Rossmore (1853–1921)
- William Westenra, 6th Baron Rossmore (1892–1958)
- William Warner Westenra, 7th Baron Rossmore (born 1931)
The heir apparent is the present holder's only son Hon. Benedict William Westenra (born 1983).