Born Guy Mastroianni to a Welsh mother and Italian/American father, he was educated at Christ's Hospital School, Sussex and then at University of Wales, Cardiff where aged 20, he graduated BSc Joint Hons in Biochemistry & Chemistry.
In 1982 he emigrated to the USA and worked in hotel restaurant management until 1984 when he became a carpenter to support acting tuition at UCLA.
Between 1985-89 he performed in over twenty plays in Los Angeles including The Caretaker (Mick), City Gents, The Elephant Man (Ross), Othello (Iago), Hamlet (Title), The Taming Of The Shrew (Petruchio), Henry V (Title), and Romeo and Juliet (Mercutio). He - regrettably - 'anglicised' his name to "Masterson" in 1986.
In 1989 he returned to the UK to attend LAMDA where he obtained a Postgraduate Diploma in Theatre. In 1991 he formed "Boy's Own Productions" (later Guy Masterson Productions) to present Peter Flannery's The Boy's Own Story on tour throughout the UK until 1993. Also, in late 1992 he appeared in Cyrano De Bergerac (Bellerose/Ligniere) with Robert Lindsay at the Theatre Royal, Haymarket, West End which ran for 9 months.
From mid 1993 until the present, he has produced and performed in solo versions of Under Milk Wood, Animal Farm, A Soldier's Song and Fern Hill & Other Dylan Thomas and American Poodle, all of which have toured extensively in the UK and on international circuits. Fern Hill premiered at Edinburgh 2001 and won himthe coveted Stage Award for Best Actor. Soon afterwards, he took the part of the Narrator in Theatr Clwyd's full cast production of Under Milk Wood, directed by Terry Hands, for their Centenary Celebration season.
In 2002 he produced and performed in an eight month 100+ performance tour of Oleanna co-starring Beth Firtzgerald, which opened at the Assembly Rooms in Edinburgh. He also presented ten additional productions that year and garnered multiple awards and nominations.
In 2003, he worked with composer (and Rolling Stones collaborator) Matt Clifford to add music & soundscape to his acclaimed production of Under Milk Wood for the Edinburgh Festival that year and then embarked on a major national tour to mark the 50th Anniversary of Dylan Thomas' death. His production of 12 Angry Men also became the biggest grossing drama of all time at the Edinburgh Fringe 2003 and, in recognition of this and of his outstanding contribution to the Fringe over 10 years, he was awarded the Jack Tinker Memorial, SPIRIT OF THE FRINGE Award. He also received a second nomination for Best Actor from the Stage for his revamped Under Milk Wood.
In February 2004, 12 Angry Men UK toured to International Festivals in Perth, Adelaide and New Zealand to huge acclaim and box office success. And for the Edinburgh Festival 2004 he directed Borge Again! with Rainer Hersch - which soon became another sell out success at Edinburgh, Winnipeg and Montreal.
Guy returned to Australia in September of the same year to direct an all-star Australian company - 12 Angry Men OZ - which played Brisbane, Sydney and Melbourne, which again broke box office records and eventually won three prestigious Greenroom Awards including Best Production and Best Direction and was nomintated for 3 Sydney Helpmann Awards.
In June 2005, Guy returned to play in London with Under Milk Wood at the Bloomsbury Theatre to great acclaim, during which run, his second daughter, Tallulah was born and his first daughter, Indigo, saw him on stage for the first time.
Edinburgh 2005, saw Guy direct The Odd Couple with Bill Bailey and Alan Davies and his company of comedians which this time smashed his own Edinburgh Fringe box office record!. He also directed Swift - a monodrama about Jonathan Swift with Jeffrey Mayhew.
In 2006 he presented Under Milk Wood at the Adelaide Fringe and then directed with Perrier Award winner Rich Hall in his first play Levelland at the Melbourne Comedy Festival and then at Edinburgh 2006 for which he also directed Cooking With Puccini again with Jeffrey Mayhew.
2007 was equally busy. Extensive UK touring was followed by a return trip to the Adelaide Fringe with Fern Hill and Under Milk Wood. Later, for Edinburgh, he presented 7 shows of which he performed in 2 and directed 4! Immediately afterwards, he directed the hugely successful The Eagle Dances starring the acclaimed Native American Ventriloquist Buddy Big Mountain and Ian Shaw for Theatr Mwydan in Cardigan.
2008 saw another return to the Adelaide Fringe with Guy presenting 5 shows including his new solo show American Poodle - together with his acclaimed productions of Playing Burton, Goering's Defence, Follow Me and of course Under Milk Wood - the latter which went on to the Gold Coast for two very popular performances. For Edinburgh he presented 3 World Premiere's and two European Premiere, directing 3 of them... During the Autumn, he embarked on a major national tour of Oleanna alongside Joanne Hartstone.
2009 yet another return to the Adelaide Fringe with Guy presenting just 2 shows; Oleanna and his solo Animal Farm to great acclaim. His Edinburgh season consisted of 6 shows including 3 world premieres including Morecambe with Bob Golding and Austen's Women. Both became sell-out hits, and Morecambe transferring to the West End over the Christmas period.
He is very proud of his extensive ties with Australia & New Zealand: Since his first appearances in NZ at Downstage Theatre in Wellington and at the Taranaki International Festival with both Under Milk Wood and Animal Farm in 1997 he has maintained a fruitful association. In 1999 he returned to NZ to present A Soldier's Song, Shylock, Animal Farm and Milk Wood for 17 city NZ national tour including 3 weeks at the Aeotea Centre in Auckland (presented by Tim Balme & Katie Wolf for Tasman Ray). In 2000, he presented Adolf at the NZ International Festival and at the Gold Coast Arts Centre in Australia. In 2001 he directed Ray Henwood in Playing Burton (which won the Chapman Tripp Best Actor Award). In 2003, he played Fern Hill at both Circa Theatre in Wellington and the Taranaki International Festival and he returned to Wellington playing Juror 4 in his own acclaimed production of 12 Angry Men at the 2004 NZ International Festival. In 2006 he presented a very successful season of Under Milk Wood at the Adelaide Fringe Festival and then directed Rich Hall's debut play, Levelland at the Melbourne International Comedy Festival. He has also very successfully presented several award winning NZ works at the Edinburgh Fringe including Tim Balme's The Ballad of Jimmy Costello (1997), Skin Tight (1998), Krishnan's Dairy & Bare (1999), No.2 (2000), Filler Up! (2001), Blowing It and The Story of Funk (2003).
Directorial credits include: Morecambe, Austen's Women, Reasonable Doubt, Scaramouche Jones, The Eagle Dances, Follow Me, Arnold Wesker's The Mistress, Levelland, The Odd Couple, Swift, 12 Angry Men (UK & OZ productions), Borge Again! Goering's Defence, A Slight Tilt To The Left, Resolution, Adolf, Mom I'm Not A Lawyer, All Words For Sex, Playing Burton (UK & NZ productions), Bye Bye Blackbird, The House Of Correction and The Private Ear & The Public Eye.
His extensive theatrical committments have largely prevented him working in other media however, notable televisual work in the UK includes Dennis Potter's Cold Lazarus and Dirty War for the BBC, several commercials and improvised comedy in Brass Eye with Chris Morris. He is currently the "Franziskaner Monk" advertising Franziskaner Weissbier in Germany, Switzerland and Austria!
As a freelance critic and feature writer he has been published in The Herald, The Guardian, The Scotsman and The Stage, The Dominion (NZ), The Times of India, and The South China Morning Post (Hong Kong).
He is married to Brigitta and father to Indigo and Tallulah.