Knockmealdown Mountains, mountain range on the border of southern County Tipperary and western County Waterford, Ireland. Formed of Devonian sandstones, and with an east-west trend, the Knockmealdowns have seven peaks with elevations higher than 2,000 feet (610 metres), the highest being Knockmealdown (2,609 feet [795 metres]). There is a very steep slope to the River Tar on the mountains’ north side, and the Caher-Lismore road crosses the range via the Gap at 1,114 feet (340 metres).