John Farley Leith, QC (5 May 1808 – 4 April 1887) was a British lawyer and Liberal politician. He was the eldest son of James Urquhart Murray Leith, of Barrach, Aberdeenshire and educated at Marischal College and Aberdeen University. He studied law at the Middle Temple and was called to the bar in 1830. He practised as a barrister in the Calcutta High Court from 1832 to 1846 and was thenProfessor of Law at the East India Company's Haileybury College from 1853 to 1857. He was made QC in 1872 and a bencher in 1874.