Talhenbont Hall (Welsh: Neuadd Talhenbont) is a Grade II listed building on a 100-acre (40 ha) estate in Gwynedd, Wales. Until it was renamed in the 19th or 20th century, the building was known as Plas Hen (Welsh for 'Old Hall').

The mansion was once part of the former estates of the Vaughan of Corsygedol family. The Vaughan family residences were inherited through marriage to the Mostyn baronets in the 18th century. In 1845, the Hall and estate were purchased by the Ellis-Nanney family. Nearby villages include Llanystumdwy to the southeast and Chwilog to the west. The Hall was originally constructed in 1607 and was further expanded in the 18th and 19th centuries. As of 2016, Talhenbont Hall has been developed as a wedding venue and its outbuildings converted into holiday cottages.

The Vaughan (Welsh: Fychan) family of Talhenbont are descendants of one of the medieval Fifteen Tribes of Wales. The first century of the Hall was turbulent because of the English Civil War. The Parliamentarian New Model Army seized the mansion, but it was later taken by the opposite side, the Royalists under John Owen, who used it as his headquarters. Owen's daughter married into the Vaughan family of Talhenbont. The Vaughan estate was once part of the largest estate in North Wales, and the same family owned the current Hall for over 200 years until it was sold in 1845. There have been several owners since.

The family of Plas Hen (today named Talhenbont) descended from Collwyn ap Tangno [cy] (c.1000 – 1050), Lord of Ardudwy and Eifionydd, founder of the 5th of the Fifteen Tribes of Wales, c. 1137. Around 1416, the family settled in the area. Madog ap Ifan ap Einion of Ystumllyn, Criccieth, grandson of Ynyr Fychan (Lord of Nannau) married the daughter of Rhys ap Tudur (Tudors of Penmynydd). Madog's grandson married an heiress of Trefan, and the property along with Plas Hen (Talhenbont) was passed from Gruffydd ap John ap Grono to their son Gruffudd ap Robert Fychan (Vaughan), who married Elizabeth of Ystumcegid and had a large family c. 1541. The property then passed to Robert Vaughan, Fychan's grandson, and it was later inherited by Robert's brother Richard (Sheriff of Caernarvonshire, 1600) of the Vaughan of Corsygedol (Cors-Y-Gedol) family.

The mansion standing today was constructed in 1607 by William Vaughan (d. 1633) of the House of Corsygedol, a dynasty started in Merionethshire by the Irishman Osbwrn Wyddel around the 13th century. William's father first constructed Corsygedol in 1576, and the Hall was extended by William in 1592, a little more than a decade before he oversaw the reconstruction of Plas Hen (Talhenbont). He married and had children with Ann Vaughan (of a different Vaughan family), heiress of Richard Vaughan of Plas Hen, Sheriff of Caernarfonshire (1600). In 1642, during the English Civil War, the owner of Talhenbont Hall, William Lloyd (Sheriff of Caernarfonshire and Ann's second husband), was arrested as a Royalist sympathiser and the New Model Army seized the Hall. Later, the mansion was used as headquarters for the Royalist army under Sir John Owen of Clenennau. Their son Richard Vaughan of Plas Hen was MP for Merioneth. In 1628, he married Owen's daughter. After successive family member-owners up until 1758, Plas Hen (Talhenbont), owned by the Vaughan family, became the largest privately owned single piece of land in the Welsh area of Eifionydd, it was also the largest estate of multiple halls and surrounding countryside in different locations in North Wales.

The last generation of Vaughan ownership began with William Vaughan (1707–1775), who attended Cambridge University. Vaughan was Custos rotulorum, and MP for Merioneth from 1734 for six parliaments until 1768. He married an heiress of the Nannau estate, Catherine Nanney, daughter of Colonel Huw Nanney, on 16 February 1733. The couple had one daughter, Anne Vaughan (1734–1767). He was buried at St Dwywe's Church, Llanddwywe. William had no male heirs, so the estate passed to his brother, Evan Lloyd Vaughan MP, the last male representative of Plas Hen. His niece Margaret, an heiress, married Sir Thomas Mostyn (6th Baronet Mostyn), and occupied the estate from 1796 onwards, as well as inheriting her estate of Corsygedol, Bodidris Hall, and Wynn family owned Bodysgallen Hall estate. Through her inheritance, the Halls passed to the family of the Mostyn baronets.

Plas Hen was later the home of William Williams. In 1845, Talhenbont Hall and surrounding land was purchased by the Ellis-Nanney family from the Mostyn baronets for £50,000 (equivalent to £7 million in 2023). The Hall became part of the Ellis-Nanney's estate of over 12,000 acres (5,000 ha). They renamed it Talhenbont Hall from Plas Hen. In 1884, the estate was split to pay debts that had accumulated during the Napoleonic Wars. The former Ellis-Nanney baronets of Gwynfryn and Cefndeuddwr estate was further broken up and sold to its tenants in 1959.