Cefn Eglwysilan is a hill in South Wales, the twin 382m summits of which lie 2 km east of Pontypridd in Rhondda Cynon Taf county borough.

Its eastern side lies within the community of Aber Valley in Caerphilly county borough.

A wireless transmission station is sited on the more northerly of the two summits (at OS grid ref ST 099911).

It is considered to mark the edge of an extensive 13th century deer park associated with nearby Caerphilly Castle.

The summit plateau of the hill is mapped as open access and thereby freely available for the public to walk.