Gwyn Pritchard was born in Yorkshire in 1948. He started composing at the age of twelve, and in 1966 entered the Royal Scottish Academy of Music where he studied the 'cello and composition. During his student years he wrote a Viola Concerto, and other works which still receive regular performances, most notably Music for Doublebass & Harp. After a short period as Director of Music at Salisbury Cathedral School he worked as a freelance 'cellist in London. He was then employed by the BBC, firstly as an orchestral 'cellist, and later to be the subject of a documentary film Young Composer for which he was also commissioned to write Spring Music. 

For a brief period he divided his time between composing and working as a ‘cellist, but in the late 1970s, after performances of Objects In Space and Mercurius at London's South Bank brought his work to the attention of a wider public, he decided to commit himself exclusively to composition and conducting. Since then much of Pritchard's compositional activity has been based outside the UK.

In 1979 Nephalauxis was performed at the Warsaw Autumn Festival. This was the beginning of a fruitful musical relationship with many Polish musicians and festivals that was to develop over the following years, culminating in his being a Featured Composer alongside Lutoslawski at the International New Music Week held in Southampton at which several of his works were performed, including the première of the major orchestral piece La Settima Bolgia. 

In 1982 he founded Uroboros Ensemble which includes some of Britain's leading instrumentalists. He has composed several pieces for the group, including Moondance, Lollay-Lollay, Chamber Concerto, Madrigal and most recently Features and Formations. As their conductor he has performed and broadcast with them throughout Britain and abroad, and as their Artistic Director has commissioned several new works, and introduced much unfamiliar music from other countries to British and other audiences in Europe.

Since the early 1990s Pritchard has developed an ongoing association with leading instrumentalists based in Switzerland (mostly in Basel) for whom he has composed a number of substantial pieces: Janus, Wayang, Break Apart, Demise (which involved him for the first time in electronics), culminating in the 'cello concerto The Fruit of Chance and Necessity which was performed in Basel at the 2004 ISCM World New Music Days. His lighthearted theatrical birthday tribute to the Basel Percussion Trio Das Mysterium der Heiligen Dreifatligket was incorporated into La Revue Burlesque by the famous Teatro Dimitri which toured in numerous countries in the late 1990s. More recently the Basel Symphony Orchestra promoted a concert which, to celebrate Pritchard's sixtieth birthday, included two of his works, and Conflux was toured extensively throughout Switzerland by the ensemble Quadriga. He has also conducted the Basel Soloists touring Britain and Canada, and Ensemble Interplay in Italy.

In recent years he has been the recipient of a number of commissions and performances in Germany, including Song for Icarus which was commissioned for the 7th Weimar Spring Days for Contemporary Music. He returned to this festival in 2008 as composer, conductor and competition judge; and in the same capacity has been invited to appear again in the 2009 festival.  2008 also saw a special concert in Essen to celebrate Pritchard’ sixtieth birthday (along with other composers' decennial anniversaries) which included all his shorter works for piano. His music has been represented regularly at the Zepernicker Randspiele in Berlin and other German festivals.

Pritchard's music is now performed around the world, and has been represented at major international festivals, in many European countries, in the USA, Canada, Hong Kong, Australia, New Zealand, and of course throughout Britain. It has also been widely broadcast, often under his own direction, on many radio and television networks. Most recently The Firmament of Time was commissioned by the BBC  and performed by the BBC Symphony Orchestra in January 2009. Current projects include a work for the Dutch group Orkest 'de ereprijs' and a piece for solo 'cello for the Italian 'cellist Giovanni Ricciardi.

In 2003 Pritchard founded the Reggello International Festival of Contemporary & Classical Music in Tuscany, Italy. As Artistic Director he invited ensembles and soloists from many parts of the world to participate, often programming music which is seldom heard in Italy. He also directed the RIF Composers' Competition, hosted by the festival. 

As a teacher and lecturer Pritchard has been invited to many academic institutions, including The Royal Academy of Music, The Birmingham Conservatoire, The Basle Conservatoire, The Eastman School of Music and several universities in Britain and American. He is a professor of composition at Trinity College of Music in London and he has also taught composition extensively to private students and in workshops in Britain and abroad. He has written, introduced and participated in programmes for BBC Radio 3, and has contributed articles and reviews to a variety of musical publications.