Sir William Pritchard or Prichard (1632?–1705) was an English merchant, slave trader and politician, Lord Mayor of London in 1682.
On 29 September 1682 he went to the poll as court candidate for the mayoralty, and on 4 October the recorder declared him third on the list, below Sir Thomas Gold and Alderman Henry Cornish, both Whigs.
When, in February 1684, proceedings were taken against him by the Whigs, he refused to appear or give bail, and on 24 April was arrested by the sheriff's officers at Grocers' Hall; he was detained in custody for six hours.
The case was tried before George Jeffreys at the Guildhall on 6 November 1684, the law-officers of the crown appearing for the plaintiff, and Serjeant John Maynard for the defendant.
His body was conveyed from his house at Highgate to Great Linford in Buckinghamshire, where it was buried on 1 March in a vault under the north aisle.
An inscription on a marble slab recorded that Prichard was president of St. Bartholomew's Hospital, and that he erected there "a convenient apartment for cutting the stone".
In Great Linford itself, the manor of which he had acquired in 1683 from the family of Richard Napier, Prichard founded and endowed an almshouse and school-buildings, and his widow increased his benefaction.