| Honorific-Prefix: | The Right Honourable |
| The Lord Rathmore | |
| Honorific-Suffix: | PC QC |
| Order1: | Paymaster General |
| Term Start1: | 24 March 1880 |
| Term End1: | 21 April 1880 |
| Monarch1: | Victoria |
| Primeminister1: | The Earl of Beaconsfield |
| Predecessor1: | Sir Stephen Cave |
| Successor1: | The Lord Wolverton |
| Order2: | First Commissioner of Works |
| Term Start2: | 24 June 1885 |
| Term End2: | 28 January 1886 |
| Monarch2: | Victoria |
| Primeminister2: | The Marquess of Salisbury |
| Predecessor2: | The Earl of Rosebery |
| Successor2: | The Earl of Morley |
| Term Start3: | 5 August 1886 |
| Term End3: | 11 August 1892 |
| Monarch3: | Victoria |
| Primeminister3: | The Marquess of Salisbury |
| Predecessor3: | The Earl of Elgin |
| Successor3: | George Shaw-Lefevre |
| Birth Date: | 1838 12, df=yes |
| Death Place: | Greenore, County Louth |
| Resting Place: | Putney Vale Cemetery, London |
| Nationality: | British |
| Party: | Conservative |
| Alma Mater: | Trinity College Dublin |
David Robert Plunket, 1st Baron Rathmore PC, QC (3 December 1838 – 22 August 1919) was an Irish lawyer and Conservative politician.
Plunket was the third son of John Plunket, 3rd Baron Plunket, second son of William Plunket, 1st Baron Plunket, Lord Chancellor of Ireland. His mother was Charlotte, daughter of Charles Kendal Bushe, Lord Chief Justice of Ireland, while the Most Reverend William Plunket, 4th Baron Plunket, Archbishop of Dublin, was his elder brother. He was educated at Trinity College Dublin[1] and was called to the Irish Bar in 1862.
After practising on the Munster Circuit for a number of years, Plunket was made a Queen's Counsel in 1868, and became Law Adviser to the Lord Lieutenant of Ireland that same year. In 1870, he was elected Conservative Member of Parliament for Dublin University, and was Solicitor General for Ireland under Benjamin Disraeli from 1875 to 1877. He was then briefly Paymaster General under Disraeli (then known as the Earl of Beaconsfield) in 1880 and was sworn of the Privy Council the same year. In 1885 he became First Commissioner of Works in Lord Salisbury's first ministry, a post he held until January 1886. He resumed the same post in August of the same year when the Conservatives returned to power, and held it until 1892. On his retirement from the House of Commons in 1895 he was elevated to the peerage as Baron Rathmore, of Shanganagh in the County of Dublin.
Apart from his political and legal career he was a director of the Suez Canal Company, Chairman of the North London Railway for many years and a director of the Central London Railway at its opening in 1900..
In Dublin, Rathmore was a member of the Kildare Street Club.[2] He died in August 1919, unmarried, at the age of eighty, in the Railway Hotel in Greenore, County Louth and is buried at Putney Vale Cemetery in London. His peerage became extinct at his death.