Sir John Trevelyan, 4th Baronet (6 February 1735 – 18 April 1828), was a British politician.
The member of an ancient Cornwall family, he was the only son of Sir George Trevelyan, 3rd Baronet, of Nettlecombe, Somerset, whom he succeeded as 4th Baronet in 1768. He also inherited Northumbrian estates from his wife's uncle in 1777.
He was appointed High Sheriff of Somerset for 1777–78 and sat as Member of Parliament for Newcastle-upon-Tyne from 1777 to 1780 and for Somerset from 1780 to 1796.
He died in April 1828, aged 93. He had married Louisa Marianne, daughter and coheiress of a Huguenot merchant, Peter Simond of London, with whom he had 6 sons and 2 daughters. His many descendants include: