John Knowles (1781 – 21 July 1841) was the English biographer of Henry Fuseli and an author of works on naval architecture.
Knowles, born in 1781, became a clerk in the surveyor's department of the navy office early in life.
Knowles died, unmarried, at Ashburton, Devonshire, on 21 July 1841, aged 60.
He was one of the original members of the Athenæum Club, and his portrait, drawn by Charles Landseer, is No.
the life of Fuseli, written as a labour of love, to which was added an edition of the painter's writings on art.