Moel y Gaer (Welsh for "bald hill of the fortress") is an Iron Age hillfort on a summit of Llantysilio Mountain, northwest of the town of Llangollen, Denbighshire, Wales.

[2] The defensive works at Moel y Gaer comprise a roughly oval area measuring about 140 metres (460 ft) east-west by 100 metres (330 ft), enclosing approximately 0.95 hectares (2.3 acres), and consist of a single rampart and a discontinuous ditch, with a single entrance on the eastern side.

[6] A track crossing the site from east to west, used by pedestrians and drivers of off-road vehicles, presents a threat to the archaeological remains.

[7] As part of the Heather and Hillforts Project a topographic survey was commissioned, which took place between December 2006 and January 2007.

[7] A geophysical survey followed in 2009, which identified more possible roundhouses, along with possible internal tracks and two potential rectangular structures.