Eglwysilan is an ecclesiastical parish and hamlet in Wales, within the community of Aber Valley in the unitary authority of Caerphilly County Borough.
During the 12th-century Norman invasion of Wales, the formal parish was defined – an area of more than 30,000 acres (47 sq mi; 120 km2), including Caerphilly.
In due course, eleven Anglican parishes were founded from it, causing a reduction in the territory remaining with the mother church.
The churchyard contains the grade II* listed tomb of the bridge builder William Edwards[5] and many of the victims of the Senghenydd Colliery Disaster of 1913.
Rice Rees offers the opinion that Ilan may have been an early Celtic saint of whom no other trace survives.