English author and adventurer, the friend of Percy Bysshe Shelley (Shelley, Percy Bysshe) and Lord Byron (Byron, George Gordon Byron, 6th Baron), whom he portrayed brilliantly in his books.

Trelawny was a handsome, dashing, and quixotic personality from an old and famous Cornish family. He was brought up in London and went to a school in Bristol, from which he ran away. At age 13 he entered the Royal Navy, and he was discharged in 1812. Trelawny wrote of his experiences as a midshipman in his semiautobiographical novel Adventures of a Younger Son (1831).

In 1822 Trelawny met Shelley (Shelley, Percy Bysshe) and Byron (Byron, George Gordon Byron, 6th Baron) in Pisa, and, after Shelley drowned at Livorno on July 8 of that year, he supervised the recovery and cremation of Shelley's body. In 1823 Trelawny accompanied Byron to Greece to aid in the struggle for Greek independence. Later Trelawny vividly recounted his friendships with the two great poets in his Recollections of the Last Days of Shelley and Byron (1858; rev. ed., Records of Shelley, Byron and the Author, 1878). From 1833 to 1835 Trelawny traveled in the United States, where, among other adventures, he attempted to swim the Niagara River between the rapids and the falls and demonstrated his sympathy for the abolitionists by buying the freedom of a slave.

Besides the Shelley circle, his friendships included Caroline Norton (Norton, Caroline), the Rossettis, Walter Savage Landor (Landor, Walter Savage), Algernon Swinburne (Swinburne, Algernon Charles), and John Millais (Millais, Sir John Everett, 1st Baronet). Trelawny's ashes were buried next to Shelley's in the Protestant Cemetery in Rome.