Tregarth is a village near Thomas Telford's A5 London to Holyhead road between the town of Bethesda and the city of Bangor in Gwynedd, north Wales.

[2] The street, Tanrhiw Road, was known locally as 'Stryd y Gynffon' (Traitor's Row or Tail Terrace) and was one of the first main settlements in the village based alongside the farmsteads of Ty'n Clawdd, Tanrhiw Isaf and Tahrhiw Uchaf.

The public house, Pant yr Ardd, was closed and put up for sale in June 2014.

Owing to Bethesda's industrial heritage, Tregarth has two railway lines running through its centre, one the Bethesda Branch Line (London and North Western Railway) which was closed in 1963 and the other The Narrow Gauge Penrhyn Quarry Railway Line which was used to transport slate from the Penrhyn Quarries to Port Penrhyn and was closed in 1962.

These lines have since been converted to the Lôn Las Ogwen cycle path as part of Sustrans Lôn Las Cymru cycle route 5[5] and take the cyclist on a journey from the Nant Ffrancon Pass winding through Tregarth down along the River Cegin towards Bangor and Port Penrhyn.