Sir John Williams QC (10 February 1777 – 15 September 1846) was an English Whig politician, lawyer and judge,^[1] known for overseeing the 1830s trials of the Tolpuddle Martyrs (R v Lovelass and Others), and the Flash Female Button Makers Union.^[2]

John Williams was educated at Trinity College, Cambridge.^[3] He was elected as a Member of Parliament (MP) for Lincoln at a by-election in March 1822,^[4][5] and held the seat until the 1826 general election, when he was returned on 9 June for Ilchester.^[6] However, that result was overturned on 22 February 1827 after an election petition,^[7] and Williams did not return to the House of Commons until February 1830, when he was returned for Winchelsea at a by-election.^[8] He held that seat until the borough was disenfranchised at the 1832 general election.^[9]

He was made a King's Counsel in Easter Term 1827.^[10] On 28 February 1834 he was made a serjeant-at-law^[11] and raised to the bench as one of the puisne barons of the Court of Exchequer, succeeding Sir John Bayley; he was knighted on 16 April 1834.^[12] On 29 April 1834 he transferred to the Court of King's Bench as puisne justice, exchanging places with Sir James Parke.^[1] He died on 14 September 1846 and was succeeded by Sir William Erle.^[13]