St Saeran's Church lies in the village of Llanynys, Denbighshire, Wales. It was listed by Cadw at Grade I on 19 July 1966 (Cadw Building ID: 808). Between 2013 and 2015 £2.5 million was spent preserving the church, which has one of the finest medieval paintings in North Wales. The church's former importance is today evidenced in the sheer size of the interior which is large and spacious; it had close links with the Bishops of Bangor, who were its "rectors" or owners. Like many Denbighshire churches it is double-naved and has a fine pair of the characteristically local late-medieval hammerbeam roofs. The fluted timber pillars between the naves are more unusual, and much later, dating from a restoration in 1768.
The church was founded in the 6th century, but the site may be of Celtic origin, and was home to a clas or religious community; it was the mother church of southern Dyffryn Clwyd (the Vale of Clwyd). Unusually, it was dedicated to Saint Saeran, a Celtic bishop-saint who also gave his name to Ffynnon Sara.