Pen-llwyn (also spelled as Penllwyn) is a hamlet in the community of Melindwr, Ceredigion, Wales, which is 72.5 miles (116.7 km) from Cardiff and 175.4 miles (282.3 km) from London. Pen-llwyn is represented in the Senedd by Elin Jones (Plaid Cymru) and is part of the Ceredigion Preseli constituency in the House of Commons.
The name derives from the welsh language meaning "the head of the grove".