The ringfort at Ellagh Beg in County Mayo survives today as a roughly D-shaped platform, its original round form interrupted on the north-west side where a modern field fence cuts clean across what the bank once described. A rath, as these earthen enclosures are generally known, was the most common type of defended farmstead in early medieval Ireland, typically consisting of a circular bank and ditch enclosing a domestic interior. Here, that enclosure has been reduced to a raised area measuring approximately 18.5 metres on its longer axis, sitting on a low rise amid sharply undulating ground, with views that are good but not wide.

The 1838 Ordnance Survey six-inch map records the site as a circular embanked enclosure, which means that whatever truncation occurred on the north-west side happened after that date. The earthwork that remains is defined on its curving side by a low scarp with a slight, sod-covered stony lip about two metres wide, more pronounced towards the north-east. The outer slope drops between half a metre and just over a metre depending on which side you measure, and the interior is largely flat, though there is a faint slump or depression running along the line of the fence where the bank was lost. The rath sits close to the south-west boundary of the Ellagh Beg townland, positioned, as many such sites were, to make modest use of natural elevation without demanding a commanding hilltop.