Gwilym was born in Llanystumdwy. He studied at Coleg Normal, Bangor and at the Birmingham College of Art. He married Claudia Williams in 1953.
They settled in Anglesey where he worked as a teacher in Llangefni, and later in Bangor.
He began to attract attention as an artist in the 1960s for his dramatic and boldly coloured paintings which distilled Wales' craggy, formidable landscapes. His new approach was bold and refreshing. During this time he exhibited regularly in London. Along the way he changed the spelling of his surname, dropping the 't', as there was another painter with the same name.
He joined the RCA in 1970, and began to paint full-time. In the 1980s he travelled widely in Europe, producing notable works in Greece and France. He settled with Claudia in Rochefort-en-Terre in Southern Brittany for many years, where they founded a school for the creative arts. He received the silver medal from the Société Académique des Artes-Sciences-Lettres in Paris in 1995. And was made an Honorary Fellow of the University of Wales in 1996.
He returned to Wales with Claudia in 1999, and settled in Tendy. In his later years he was regarded as Wales' most senior and noteworthy landscape painter. He had a major exhibition in Cardiff, and a monograph, in 2013.
He exhibited widely in Wales and abroad. His work is held in several Public Collections, including the Aberystwyth University, the Welsh Arts Council and CASW.
An exhibition of paintings by Gwilym Prichard will be held on the 17th April 2026.