Viscount Mountgarret is a title in the Peerage of Ireland.
The title was created in 1550 for the Hon. Richard Butler, younger son of Piers Butler, 8th Earl of Ormond.
His grandson, the third Viscount, was outlawed and excepted from pardon in 1652, one year after his death. His son, the fourth Viscount, received a pardon for all treasons and rebellions from King Charles II and was restored to his estates.
He was succeeded by his son, the fifth Viscount who was a supporter of King James II and led the siege of Derry in 1688 to 1689. Lord Mountgarret was taken prisoner and outlawed, with his estates forfeited. However, in 1715 the outlawry was reversed and in 1721 he claimed his seat in the Irish House of Lords.
- Edmund Butler, 2nd Viscount Mountgarret (died 1602)
- Richard Butler, 3rd Viscount Mountgarret (1578–1651)
- Edmund Butler, 4th Viscount Mountgarret (1595–1679)
- James Butler, 8th Viscount Mountgarret (1686–1749)
- Edmund Butler, 9th Viscount Mountgarret (1687–1751)
- Edmund Butler, 12th Viscount Mountgarret (1771–1846) (created Earl of Kilkenny in 1793)
Earls of Kilkenny (1793)
- Edmund Butler, 1st Earl of Kilkenny, 12th Viscount Mountgarret (1771–1846)
- Henry Edmund Butler, 14th Viscount Mountgarret (1844–1912)
- Piers James Richard Butler, 18th Viscount Mountgarret (b. 1961)