O'BRIEN, Murrough, 5th Earl of Inchiquin [I] (1726-1808), of Taplow, Bucks.

Published in The History of Parliament: the House of Commons 1754-1790, ed. L. Namier, J. Brooke., 1964
Available from Boydell and Brewer



1784 - 1796
6 Nov. 1797 - Dec. 1800

Family and Education

b. 1726, 1st s. of Hon. James O’Brien (3rd s. of William, 3rd Earl of Inchiquin), by Mary, da. of Rev. William Jephson, dean of Kilmore.  m. (1) 5 Mar. 1753, cos. Lady Mary O’Brien (suc. mother as Countess of Orkney [S] 7 Dec. 1756, d. 10 May 1790), da. of William, 4th Earl of Inchiquin, by Lady Anne Hamilton, da. of George, 1st Earl of Orkney, s.j. Countess of Orkney 1737, 1da.; (2) 25 July 1792, Mary, da. of John Palmer of Torrington, Devon by Mary, sis. of Sir Joshua Reynolds, s.p.  suc. fa. 1771; uncle William, 4th Earl of Inchiquin 18 July 1777; P.C. [I] 23 Dec. 1780; K.P. 5 Feb. 1783; cr. Mq. of Thomond [I] 29 Dec. 1800 with sp. rem. to heirs of his bro.; Baron Thomond [UK] 2 Oct. 1801.

Offices Held

M.P. [I] 1757-68.

Ensign 1 Ft. Gds. 1743, capt. 1747, ret. 1756.


In 1777 Inchiquin inherited with his uncle’s title an estate said to bring him £9,000 a year.1 In September 1779, it was rumoured that he would stand at the Buckinghamshire by-election. Though it had ‘long been an object with Lord Inchiquin to represent Buckinghamshire’, Edmund Burke wrote to the Duke of Portland, 24 Sept., yet ‘on a full consideration of the present state of his finances ... he resolved unless called upon, and called upon singly, he would not risk a contest which even attended with victory would be ruinous’. But to prevent the county from becoming an ‘heirloom’ of the Grenville family, he was looking for an independent candidate. On the other hand, William Burke wrote to Portland, 28 Sept.: ‘Lord Inchiquin will most probably be in the nomination. ... He is as yet precluded from making his application to your Grace, or any one, but hopes that your Grace will be open to him when he is at liberty to entreat the honour of your support, and in truth if ever man had claim to the support of the Whigs it is Lord Inchiquin.’ In the end Inchiquin did not stand: ‘He could only come in on the destruction of Lord Verney, which was a thing impossible’, Edmund Burke wrote to Portland, 16 Oct. 1779.

In 1784 Inchiquin was returned for Richmond by Thomas Dundas. He was classed as ‘Opposition’ by William Adam, May 1784; voted for parliamentary reform, 18 Apr. 1785; and with the Opposition on Richmond’s fortifications plan, 27 Feb. 1786. When in March 1786, it was rumoured that a number of Irish marquesses were to be created, Inchiquin wrote to the Duke of Rutland asking that his family ‘from ... its many services to the Government’ might be ‘considered entitled to that mark of favour’.2 Inchiquin voted with the Opposition on the Regency, 1788-9. He seems not to have spoken in the House before 1790.

He died 10 Feb. 1808.

Ref Volumes: 1754-1790

Author: Mary M. Drummond


  • 1. HMC Carlisle, 322.
  • 2. HMC Rutland, iii. 288.