Tanfield Vachell (1602–1658) was an English politician who sat in the House of Commons between 1645 and 1653.
Vachell was the son of John Vachell of Warfield and his wife Mary Vincent, daughter of Clement Vincent of Peckleton, Leicestershire. He was baptised Gayton, Northamptonshire on 27 December 1602. He was educated at Exeter College, Oxford, taking BA in 1622.
His uncle, Sir Thomas Vachell of Coley Park in Reading, Berkshire, who had married three times and had no issue, wanted someone of his name and blood to inherit the Vachell estates which had become concentrated upon him. Vachell was therefore persuaded to marry and after the uncle’s death in 1638, Vachell inherited the estates. He was High Sheriff of Berkshire in 1641.
Vachell was also influenced by his uncle's widow, Lady Letitia (née Knollys) Vachell who married John Hampden, and supported the Parliamentary cause during the Civil War. Lady Vachell carried on living at Coley Park, whilst Tanfield rented the Reading home of her grandfather at Abbey House. On 1 November 1642, the King gave instructions for Vachell to escort him through the county, but as this had previously been an excuse to disband local militia, Vachell refused to obey.
In 1645, Vachell was elected Member of Parliament for Reading in a disputed election to the Long Parliament.
Vachell was more concerned with arts than politics and built a collection of rare pictures, books and curios. His portrait was painted by Sir Peter Lely. In around 1651, he restored Coley Park.
Vachell died at Reading in May 1658 and was buried in St Mary's Church in Reading on 1 June 1658.