Welsh Bicknor (Welsh: Llangystennin Garth Brenni) is an area of Herefordshire known as a detached parish (exclave) of the traditional county of Monmouthshire.

The manor house and surrounding land of Welsh Bicknor were seized from Richard Vaughan in 1651 because he was a Catholic and given to Phillip Nicholas of Llansoy , in Monmouthshire. This is how the rather unusual situation of the exclave occurred.

It has been deemed to be part of Herefordshire for administrative purposes since an Act of Parliament of 1844.

As its name suggests, Welsh Bicknor has close ties with Wales, being a detached parish of Monmouthshire, although adjacent to English Bicknor, which is part of Gloucestershire. The Manor House of Welsh Bicknor, known as Courtfield, belonged originally to the Vaughn family. However, in 1651 Richard Vaughn, who was a Catholic, had his land sequested and given to Phillip Nicholas of Llansoy, in Monmouthshire.

Religious dissension within the Vaughn families continued for several generations. In 1715, a John Vaughan (presumably one of Richard's descendants) refused the oath of allegiance to George I. He had estates in the several counties of Monmouthshire, Radnorshire, Herefordshire, and Gloucestershire valued at £1,000 per annum. In 1719 he was fined for not attending church.

A later generation, in the person of Richard Vaughan, joined Prince Charles Edward Stuart's Army in 1745. Vaughan took part in the battle of Culloden and followed the Prince into exile. He and his brother William Vaughan were outlawed and their property seized, while they themselves fled to Spain and became officers in the army of that country. Both married Spanish Ladies and some of their descendants settled in the home of their adoption and became grandees of Spain.

Richard Vaughan died in Barcelona in 1795 but his son William eventually returned to Wales and obtained a restoration of the main portion of his estates, as heir to his uncle. Finally, John Vaughan of Courtfield, elder brother of William took the oath of allegiance to King George III at Monmouth in 1778.

Welsh Bicknor was therefore administratively considered to have been returned to Herefordshire by two acts of Parliament passed respectively in the reigns of William IV and Victoria (1844). Welsh Bicknor parish records are now held by Hereford Records Office.

Much of the above is based on information kindly supplied by:- Harold Watkins, of Perth, Western Australia.