Knocknahillion (, meaning peak of the west elbow) at , is the 210th-highest peak in Ireland on the Arderin scale, and the 256th-highest peak on the Vandeleur-Lynam scale. Knocknahillion is situated in the middle sector of the long north-west to south-east cental spine of the Maumturks mountain range in the Connemara National Park in County Galway, Ireland. The summit is offset to the west of the rocky central ridge of the Maumturks, and its western facing slopes have a distinctive diagonal rock stratification when viewed from the Inagh Valley.