William Mathias was born in Whitland, Dyfed. He studied at the University College of Wales, and subsequently at the Royal Academy of Music. From 1970-1988 he was Head of the Music Department at the University College of North Wales, Bangor.
Mathias's musical language embraced both instrumental and vocal forms with equal success, and he addressed a large and varied audience both in Britain and abroad. He was also known as a conductor and pianist, and gave or directed many premières of his own works. He was made CBE in the 1985 New Year's Honours.
In 1992, the year of his death, Nimbus Records embarked upon a series of recordings of his major works.