John Twynyho (c.1440 - 30 September 1485) (alias Twynyhoe, Twynihoe, etc.) of Cirencester, Bristol and Lechlade, all in Gloucestershire, was a lawyer and wealthy wool merchant who served as Recorder of Bristol, as a Member of Parliament for Bristol in Gloucestershire in 1472-5 and in 1484 and for the prestigious county seat Gloucestershire in 1476. In 1478 he was Attorney General to Lord Edward (the future King Edward V (1483-1483)), eldest son and heir of King Edward IV.
He was the second son of William Twynyho of Keyford (today the "Old Nunnery", Lower Keyford), near Frome in Somerset, by his wife who was a daughter and co-heiress of the Cobington family. John Twynyho's sister-in-law Ankaret Hawkeston, the wife of his elder brother William Twynyho of Keyford, had been a servant of Isabel Neville, Duchess of Clarence (died 1476), a daughter and co-heiress of Richard Neville, 16th Earl of Warwick (1428-1471) The Kingmaker, whose death in childbirth had been blamed by her husband George Plantagenet, 1st Duke of Clarence (executed 1478), on a poisoning by Ankaret. Clarence was determined to have Ankaret executed, against the wishes of the Queen, who believed her to be an elderly and harmless widow blamed unjustly. Clarence rapidly gave orders for her arrest, which was performed at her home at Keffordthe family home, on 12 April 1477 by Richard Hyde and Roger Strugge and 80 "riotous persons", whence she was taken to Bath, thence to Cirencester thence to Warwick, where she was tried before Justices of the Peace at Warwick Guildhall and found guilty by a jury. She was hanged at Mytton, Warwickshire on 15 April 1477, which action is considered by modern historians to have been a notorious judicial murder. Clarence himself was executed in the Tower of London the following year, on 18 February 1478, and two days later on 20 February 1478 Ankaret's grandson Roger Twynyho obtained the king's annulment of Ankaret's conviction.