Patrick Robin Gilbert Vanden-Bempde-Johnstone, 4th Baron Derwent CBE (26 October 1901 – 2 January 1986), was a British peer and Conservative politician.

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.

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.

He died on 2 January 1986, aged 84, and was succeeded in the barony by his son Robin Evelyn Leo Vanden-Bempde-Johnstone.