Defynnog, also known as Devynock in some historical documents, is a small village in the community of Maescar in the historic county of Breconshire (Brecknockshire), now lying within the county of Powys, Wales. It lies immediately south of Sennybridge and about ten miles west of Brecon within the Brecon Beacons National Park.
An important place in the past, Defynnog lost much of its importance as Sennybridge became more developed. The village (which has also been referred to historically as 'Devynnock') is located in the Brecon Beacons National Park one mile south of Sennybridge, beside the Afon Senni just south of its confluence with the River Usk and where the A4215 road meets the A4065. The Welsh name signifies the 'territory belonging to Dyfwn'.
The local church, dedicated to Saint Cynog, contains an ancient stone with Ogham inscriptions and is a grade I listed building. In 1836 a chapel in the parish of Defynnog was dedicated to Saint Callwen.
In 2014, a Yew (Taxus baccata) found in the churchyard was estimated to be five thousand plus years old. It has been subject to extensive investigation, including dendrochronology, and DNA analysis. The crown of the tree is 60 ft in diameter.
The rectory within the Church grounds was once the property of Moses Williams FRS and his inscription is to found on the beams of one of the attics. The property immediately south of the lychgate (Ty Defynnog, Defynnog House) is probably made up of two former cottages. Its cellar contains a stone slab of uncertain purpose. It is a Grade II listed building
The Sir John Davy School is now a cafe and antiques centre. The Sir John Davy Alms houses are sited close to a former police station and court, later a brass rubbing centre and now a bed and breakfast, complete with police cells. Dewi Davies' book (p. 151) contains an account of sheep stealing in Defynnog.
- Barnes, David (2005). The Companion Guide to Wales. Companion Guides. p. 93. ISBN 978-1-900639-43-9.
- "Ordnance Survey map 141: Brecon". One inch series. Ordnance Survey.
- Ordnance Survey Explorer map OL12 'Brecon Beacons National Park: western area'
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- "Church of Saint Cynog, Maescar". British Listed Buildings. Retrieved 17 December 2013.
- Rees, Rice (1836), An Essay on the Welsh Saints Or the Primitive Christians, Usually Considered to Have Been the Founders of the Churches in Wales, Longman, Rees, Orme, Brown, Green, and Longman, p. 153, retrieved 2016-04-07
- "5000 years and counting". Woodlands.co.uk. Retrieved 29 April 2016.
- Ingham, John (8 July 2014). "Found yew! The 'oldest tree in Europe' discovered in a Welsh cemetery". Express. Retrieved 29 April 2016.
- Reilly, Rachel (7 July 2014). "'Britain's oldest tree' is discovered in a Welsh churchyard - and it's more than FIVE THOUSAND years old". MailOnline. Retrieved 29 April 2016.
- "Defynnog House / Ty Defynnog, Maescar". British Listed Buildings. Retrieved 28 April 2016.
- "Cold War Warrior's photos with the Organist". ipernity. Retrieved 28 April 2016.
- "Sir John Davy School; Alms houses, Defynnog". Coflein. Royal Commission of the Ancient and Historical Monuments of Wales. Retrieved 28 April 2016.
- "Law and Disorder in Breconshire", Dewi Davies, published by D.G and A.S. Evans, Brecon.