Knockboy is a Hewitt of 704.8 m in Cork, Kerry. It is the highest of the 3 register hills recorded in Cork, Kerry; the next is Knockowen at 660.3 m, 44.5 m lower.
It is also on the county tops list, as the highest point of its historic county. The key col lies 81.2 km away to the north-east, at 96 m. Its drop of 609 m is 86% of its height: the col linking it to higher ground is only 96 m above sea level. It shares its height of 704.8 m with Corra-bheinn. The summit is marked by a trig point.