William Gwenlyn Parry (1932 – 5 November 1991) was a Welsh dramatist. Parry was author of several prominent Welsh plays including Saer Doliau (1966), Ty ar y Tywod (1968), Y Ffin (1973), Panto, Sal and Y Tŵr (1978).
Gwenlyn Parry was born in the Welsh slate-quarrying village of Deiniolen, Caernarfonshire (Gwynedd).
Initially working as a teacher, Parry taught Mathematics at a school in London and later Science through the medium of Welsh in Bethesda, Wales. Parry joined BBC Wales in 1966 and helped to establish the scripts department, where he worked on popular Welsh programmes such as Pobol y Cwm. He also achieved writing credits for the TV play Grand Slam and the feature film Un Nos 'Ola Leuad (based on the book by Caradog Prichard).
Parry's early work has been called Absurdist.
He was married twice, first to Joy and then to Ann Beynon. He had two daughters from his first marriage and a son and a daughter from his second. He died in the Cardiff area of south Wales in 1991. He is buried in Macpela, Penygroes, Gwynedd.