Pwllheli is a market town and community on the Llŷn Peninsula, north-west Wales. It lies in the traditional county of Caernarfonshire but is currently administered as part of the unitary authority of Gwynedd. It had a population of 4,076 in 2011, the population declining slightly to 3,947 in 2021. of whom a large proportion, 81%, were Welsh speaking. Pwllheli is the place where Plaid Cymru was founded. It is the birthplace of the Welsh poet Sir Albert Evans-Jones.

The Llŷn Peninsula extends 30 miles (50 km) into the Irish Sea from North West Wales, south west of the Isle of Anglesey. It is part of the historic county of Caernarfonshire, and historic region and local authority area of Gwynedd. Much of the eastern part of the peninsula, around Criccieth, may be regarded as part of Eifionydd rather than Llŷn, although the boundary is somewhat vague. The area of Llŷn is about 400 km2 (150 sq mi), and its population is at least 20,000.