John Thornhill JP (14 July 1815 – 28 January 1875) was an English first-class cricketer and clergyman.

The son of the politician George Thornhill, he was born in July 1815 at Hemingford Grey, Huntingdonshire. He was educated at Rugby School,^[1] before going up to St John's College, Cambridge.^[2] After graduating from Cambridge, he took holy orders in the Anglican Church, being ordained as a deacon at Durham Cathedral in 1838. His first ecclesiastical post was at Boxworth in Cambridgeshire, where he was appointed reverend in 1839.^[2] Thornhill was from a cricketing family, with his brothers Charles and George both playing first-class cricket. Thornhill himself played two first-class matches for the Marylebone Cricket Club, both against Cambridge University at Cambridge in 1840 and 1842.^[3] He scored 19 runs in his two matches, with a highest score of 8.^[4] From 1850 he was concurrently the reverend of Childerley, a hamlet to the south of Boxworth.^[2] Thornhill was also a justice of the peace for Cambridgeshire. He died at Boxworth in January 1875.^[5]