Llaneuddog is a hamlet in the community of Llaneilian, Anglesey, Wales. It lies along the A5025 road, between Brynrefail and Penysarn, near Dulas. It belonged to the historical parish of Llanwenllwyfo, now part of Llaneilian. The hamlet takes its name from an ancient chapel to St Euddog which was in the vicinity of the A5025. It was recorded in 1920 as having the stones re-used in farm buildings, and the water stoup used as a pig trough at nearby Lligwy. The presumed site is a small enclosure with a crescent-shaped bank thought to be the churchyard boundary.