Penllyn may refer to the following places:
United States Penllyn, a village in Lower Gwynedd Township, Montgomery County, Pennsylvania
Wales Penllyn, Gwynedd, a former civil parish in Gwynedd (1894–1974) Penllyn, Vale of Glamorgan, a village and community in the Vale of Glamorgan Penllyn (cantref), an ancient cantref of Gwynedd
See also Penllyn railway station (disambiguation) Pen-Llyn, Anglesey Llŷn Peninsula, Gwynedd, known in Welsh as