| Honorific-Prefix: | The Right Honourable |
| The Lord Derwent | |
| Honorific-Suffix: | CBE |
| Office2: | Minister of State for Home Affairs |
| Monarch2: | Elizabeth II |
| Primeminister2: | Sir Alec Douglas-Home |
| Term Start2: | 23 October 1963 |
| Term End2: | 16 October 1964 |
| Predecessor2: | The Earl Jellicoe |
| Successor2: | Alice Bacon |
| Office3: | Minister of State for Trade |
| Term Start3: | 6 September 1962 |
| Term End3: | 23 October 1963 |
| Monarch3: | Elizabeth II |
| Primeminister3: | Harold Macmillan |
| Predecessor3: | Alan Green |
| Successor3: | The Lord Drumalbyn |
| Office15: | Member of the House of Lords Lord Temporal |
| Term Start16: | 13 January 1949 |
| Term End16: | 2 January 1986 Hereditary peerage |
| Predecessor16: | The 3rd Baron Derwent |
| Successor16: | The 5th Baron Derwent |
| Birth Date: | 26 October 1901 |
| Party: | Conservative Party |
Patrick Robin Gilbert Vanden-Bempde-Johnstone, 4th Baron Derwent (26 October 1901 – 2 January 1986), was a British peer and Conservative politician.
Derwent was the younger son of Hon. Edward Henry Vanden-Bempde-Johnstone, younger son of Harcourt Vanden-Bempde-Johnstone, 1st Baron Derwent. His mother was Evelyn Mary Agar-Ellis. He was educated at Sandroyd School then Charterhouse School. He succeeded as fourth Baron Derwent on the death of his elder brother, George Harcourt Vanden-Bampde-Johnstone, 3rd Baron Derwent, in 1949 and took his seat in the House of Lords. In September 1962, Derwent was appointed Minister of State for Trade in the Conservative government of Harold Macmillan, and when Sir Alec Douglas-Home became Prime Minister in October 1963 he was promoted to Minister of State for Home Affairs. He retained this post until the Conservative loss in the 1964 general election. He never held ministerial office again but served for many years as a Deputy Speaker in the House of Lords.
Lord Derwent married Marie-Louise Henriette Picard, daughter of Albert Picard of Paris, France, in 1929. He died on 2 January 1986, aged 84, and was succeeded in the barony by his son Robin Evelyn Leo Vanden-Bempde-Johnstone.