Penmaen is a hamlet and community in Caerphilly county borough, south Wales, within the historic boundaries of Monmouthshire. It is situated in the Sirhowy valley, 3 miles East of Blackwood. It is contiguous with, if not completely encompassed by, the larger village of Oakdale, which forms most of the community urban area. Penmain is an anglicisation of the Welsh language name Penmaen, meaning quite simply "headland" or "outcrop".