After training at London's Royal Academy of Dramatic Art (RADA), he worked mainly in theatre throughout the 1990s with stage roles in Romeo and Juliet (1992), Don't Fool with Love (1993), Peer Gynt (1994), The Seagull (1995), The Homecoming (1997), and Henry V (1997).

[12] Sheen was raised in a theatrical family; his parents were both involved in local amateur operatics and musicals[13] and, later in life, his father worked as a part-time professional Jack Nicholson lookalike.

[13] He moved to London in 1988 to train as an actor at the Royal Academy of Dramatic Art (RADA),[13] having spent the previous year working in a Welsh fast-food restaurant called Burger Master to earn money.

The Times praised Sheen's "astonishing vitality"[33] while The Independent found him "sensationally good" and noted that "the Norwegian press were grudgingly captivated by the mercurial Welsh boyo".

[41] Sheen's most significant appearance of 1997 was the title role in Henry V, staged by the Royal Shakespeare Company (RSC) at their Stratford-upon-Avon theatre, which earned him a second Ian Charleson Award nomination.

[49] In early 1998 Sheen formed a production company, The Foundry, with Helen McCrory and Robert Delamere to promote the work of emerging playwrights,[48] and produced A Little World of Our Own at the Donmar Warehouse, which gave Colin Farrell his West End debut.

"[57] The Financial Times noted: "As Jimmy Porter, a role of staggering difficulty in every way, Michael Sheen gives surely the best performance London has yet seen from him ... You hang on every word he utters ...

Sheen played a gay aristocrat in an ensemble cast which included James McAvoy, Emily Mortimer, David Tennant, Dan Aykroyd, Jim Broadbent and Peter O'Toole.

The Channel 4 film explored the so-called Granita pact made by Tony Blair and Gordon Brown prior to the 1994 Labour Party leadership election, and was the actor's first collaboration with screenwriter Peter Morgan.

[91][92] In addition, he had a supporting role in Ridley Scott's Kingdom of Heaven,[93] made a cameo appearance in The League of Gentlemen's Apocalypse[94] and starred in the short film The Open Doors.

The film focused on the differing reactions of the British Royal Family and the newly appointed Prime Minister following the death of Diana, Princess of Wales in 1997; it was Sheen's third collaboration with director Stephen Frears and his second with screenwriter Peter Morgan.

The play, written by Peter Morgan, directed by Michael Grandage and co-starring Frank Langella, was a critical and commercial success[108] but Sheen initially accepted the role as a favour to his friends and "never thought it was going anywhere".

[110] "He's got the voice, the mannerisms, the blaze," said the Financial Times, "but, more than that, Sheen – as viscerally exciting an actor as any in Britain today – shows us the hunger of Frost's ambition .. and fox-like instinct for the hunt and the kill.

[114] Variety said his performance was "remarkable.. utterly convincing",[115] USA Today found him "outstanding"[116] while the Los Angeles Times felt he was "reminiscent of Daniel Day-Lewis in My Left Foot, bringing a vibrancy and wit to the role".

[117] Also that year, Sheen starred in the short film Airlock, or How To Say Goodbye in Space with Derek Jacobi[118] and was invited to join the actors' branch of the Academy of Motion Picture Arts & Sciences.

"[131] The New York Times felt he was "the movie's greatest asset ... [taking] a lively break from his usual high-crust duties to bring wit, actual acting and some unexpected musculature to the goth-horror flick".

[135] In its review, Rolling Stone said: "Late in the film, a real actor, Michael Sheen, shows up as the mind-reading Aro, of the Italian Volturi vampires, and sparks things up.

[145] In other 2010 film work, Sheen voiced Nivens McTwisp, the White Rabbit, in Tim Burton's Alice in Wonderland[146] and Dr. Griffiths in Disney's Tinker Bell and the Great Fairy Rescue[147] and appeared as a terrorist in Unthinkable.

[148] On television, Sheen's performance in the third instalment of Peter Morgan's Blair trilogy, The Special Relationship, was nominated for an Emmy Award for Outstanding Lead Actor – Miniseries or Movie.

[174] In 2012 film work, Sheen starred opposite Toni Collette in the independent comedy Jesus Henry Christ[175] and reprised his role as the vampire Aro in the final instalment of The Twilight Saga.

[187][188] The Guardian described him as "fascinating to watch ... intelligent, inventive and full of insights ... [he] delivers the "What a piece of work is a man" passage with a beautiful consciousness of human potential.

"[190] In 2013, Sheen appeared in a supporting role as the boyfriend of Tina Fey in the comedy Admission, with Stephanie Zacharek of The Village Voice describing the character as "a whiskery, elfin academic who chuckles to himself as he reads the Canterbury Tales prologue aloud in bed, in Middle English, no less.

[192] R. Kurt Osenlund of Slant Magazine said "the ever-versatile Sheen brings an artful hamminess to his role"[193] but Matt Pais of RedEye found him "insufficiently zany" in "a part that Robert Downey Jr. would nail but never accept.

[197][198][199] Anthony Lane of The New Yorker remarked: "How you prevent such a fellow, crushed by his own decency, from sagging into a bearded Ashley Wilkes is no easy task, yet Sheen succeeds, and Boldwood's brave smile grows dreadful to behold.

"[201] Peter Bradshaw of The Guardian remarked that Sheen's face "is etched with agony and an awful kind of abject adoration, forever trying to find ways to forgive the loved one in advance for rejection.

[217] He and Lizzy Caplan portrayed the 1960s human sexuality pioneers Masters and Johnson; the series chronicled "their unusual lives, romance and pop culture trajectory, which saw them go from a Midwestern teaching hospital to the cover of Time magazine and Johnny Carson's couch".

[236] In May 2019 Sheen starred alongside David Tennant in Good Omens, based on the novel of the same name written by Terry Pratchett and Neil Gaiman and was cast as Chris Tarrant in the TV adaptation of James Graham's stage play Quiz.

[273] Sheen is a patron of British charities, including Scene & Heard,[274] NSPCC's Child's Voice Appeal,[275] Healing the Wounds,[276][277] The Relationships Centre,[278] WGCADA (West Glamorgan Council on Alcohol and Drug Abuse)[279] and Adferiad Recovery, a new organisation providing support for vulnerable people in Wales and their families and carers.

[304][305] He did not publicly announce the move, but fans discovered it when they spotted Facebook posts in local community groups from a television production company called Full Fat TV.

[406] He has narrated six novels for BBC Radio 4 and Naxos AudioBooks: Crime and Punishment (1994),[407] The Idiot (1995),[408] The Picture of Dorian Gray (1995),[409] A White Merc With Fins (1997),[410] Salmon Fishing in the Yemen (2011)[411] and The Ocean at the End of the Lane (2013).