Knocknahillion is one of the Maumturk Mountains of Connemara in County Galway, Ireland. At 607 metres (1,991 ft), it is the 210th–highest peak in Ireland on the Arderin list, and 256th–highest on the Vandeleur-Lynam list. Knocknahillion is in the middle sector of the long north-west to the south-east spine of the Maumturks. 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.