The first creation was for Walter Blount, who summoned to Parliament as Baron Mountjoy in the Peerage of England in 1465. The 8th Baron Mountjoy was created Earl of Devon in 1603 and died without legitimate issue in 1606, when the earldom and the barony became extinct. His son Mountjoy Blount, who had been born before his parents' marriage, was created Baron Mountjoy of Mountjoy Fort in the Peerage of Ireland in 1618, Baron Mountjoy of Thurveston in the Peerage of England in 1627 and Earl of Newport in the Peerage of England in 1628. All these titles became extinct with the death of the 3rd Earl of Newport in 1681. Elizabeth Blount, sister of the 2nd Baron Mountjoy of the 1465 creation, had married the 1st Baron Windsor, and their descendant Thomas Windsor, 1st Viscount Windsor in the Peerage of Ireland and younger son of the 7th Baron Windsor and 1st Earl of Plymouth, was created Baron Mountjoy in the Peerage of Great Britain in 1712. This title became extinct on the death of his son the 2nd Viscount Windsor in 1758. Charlotte Jane Windsor, daughter of the 2nd Viscount Windsor and 2nd Baron Mountjoy, married the 4th Earl of Bute, and that nobleman was created Marquess of Bute, Earl of Windsor and Viscount Mountjoy in the Isle of Wight in 1796, in the Peerage of Great Britain. These titles remain extant.

The titles of Viscount Mountjoy and Baron Stewart of Ramelton in the Peerage of Ireland were conferred upon Sir William Stewart, 3rd Baronet, of Ramelton, in 1683. His grandson the 3rd Viscount Mountjoy was created Earl of Blessington in 1745 and died in 1769, when all his peerage titles became extinct (though the baronetcy remains extant). His cousin Anne, daughter of the Hon. Alexander Stewart and granddaughter of the 1st Viscount Mountjoy, married in 1711 Luke Gardiner, who served as Vice-Treasurer of Ireland. Their grandson Luke was created Baron Mountjoy in 1789 and Viscount Mountjoy in 1795, both in the Peerage of Ireland. His son the 2nd Viscount Mountjoy was created Earl of Blessington, again in the Peerage of Ireland, in 1816. His second wife was the famous Maguerite, Countess of Blessington. He died without male issue in 1829, when all his titles became extinct.

Contents [hide]
1 Barons Mountjoy (1465)
2 Barons Mountjoy of Mountjoy Fort (1618) and Mountjoy of Thurveston (1627)
3 Viscounts Mountjoy (1683)
4 Barons Mountjoy (1789) and Viscounts Mountjoy (1795)
5 Viscounts Mountjoy (1796)
6 References
 
 

 Barons Mountjoy (1465)
Walter Blount, 1st Baron Mountjoy (1420-1474)
Edward Blount, 2nd Baron Mountjoy (1467-1475)
John Blount, 3rd Baron Mountjoy (1445-1485)
William Blount, 4th Baron Mountjoy (1478-1534)
Charles Blount, 5th Baron Mountjoy (1516-1544)
James Blount, 6th Baron Mountjoy (d. 1581)
William Blount, 7th Baron Mountjoy (1561-1594)
Charles Blount, 8th Baron Mountjoy (1562-1606), created Earl of Devon(shire) in 1603

[edit] Barons Mountjoy of Mountjoy Fort (1618) and Mountjoy of Thurveston (1627)
Mountjoy Blount, 1st Baron Mountjoy (1597-1665), created Earl of Newport in 1628
Mountjoy Blount, 2nd Baron Mountjoy, 2nd Earl of Newport (1630-1674)
Thomas Blount, 3rd Baron Mountjoy, 3rd Earl of Newport (d. 1675)
Henry Blount, 4th Baron Mountjoy, 4th Earl of Newport (d. 1679)

 Viscounts Mountjoy (1683)
William Stewart, 1st Viscount Mountjoy (1653-1692)
William Stewart, 2nd Viscount Mountjoy (1675-1728)
William Stewart, 3rd Viscount Mountjoy (1709-1769), created Earl of Blessington in 1745

[edit] Barons Mountjoy (1789) and Viscounts Mountjoy (1795)
Luke Gardiner, 1st Viscount Mountjoy (1745-1798)
Charles John Gardiner, 2nd Viscount Mountjoy (1782-1829), elected a representative peer in 1809, created Earl of Blessington in 1816

 Viscounts Mountjoy (1796)
John Crichton-Stuart, 1st Viscount Mountjoy, 1st Marquess of Bute (1744-1814)
John Crichton-Stuart, 2nd Viscount Mountjoy, 2nd Marquess of Bute (1793-1848)
John Crichton-Stuart, 3rd Viscount Mountjoy, 3rd Marquess of Bute (1847-1900)
John Crichton-Stuart, 4th Viscount Mountjoy, 4th Marquess of Bute (1881-1947)
John Crichton-Stuart, 5th Viscount Mountjoy, 5th Marquess of Bute (1907-1956)
John Crichton-Stuart, 6th Viscount Mountjoy, 6th Marquess of Bute (1933-1993)
John Crichton-Stuart, 7th Viscount Mountjoy, 7th Marquess of Bute (b. 1958)

 References
Leigh Rayment's Peerage Page