The former "Harry Potter" star plays the title role in a Michael Grandage-directed production of McDonagh's scabrous tragicomedy at London's Noel Coward Theatre.
First staged in 1996, the play is a raucously dark take on Irish identity from the writer-director of plays including "The Beauty Queen of Leenane" and movies "In Bruges" and "Seven Psychopaths."
Radcliffe stars as Billy, a 17-year-old orphan on a remote island in 1930s Ireland, who sees a chance of escape from a life of boredom and mockery when an American film crew arrives on a neighboring island to shoot the film "Man of Aran."The 23-year-old actor had to master the part's taxing physical demands, its emotional shifts - and a strong Irish accent.
The Guardian's Michael Billington said Wednesday the performance proved that Radcliffe "is a fine stage actor with a gift for playing social outsiders," while Times of London critic Libby Purves praised his "still, melancholy intensity and resolve."
In The Independent newspaper, Paul Taylor hailed Radcliffe's "honest, sensitive, unshowy performance" - though he said "Radcliffe may not have the most convincing Irish accent in Grandage's vividly quirky ensemble."
"Unlike many child stars, Daniel Radcliffe has grown up gracefully," said the Daily Telegraph's Charles Spencer, who thought "the former boy wizard lends this disconcertingly cruel play what little heart it has."
Radcliffe has taken on a series of challenging stage and screen roles as he's moved on from a decade as J.K. Rowling's magical hero.
"I didn't just want to take an easy way out of this," he told The Associated Press in a March interview. "I wanted to really try and take risks and make a career for myself."
His 2007 stage debut in Peter Shaffer's "Equus" required him to bare all, emotionally and physically. He made his Broadway debut singing and dancing in the musical "How To Succeed in Advertising Without Really Trying."
His movie roles have included Beat poet Allen Ginsberg in "Kill Your Darlings" and a bereaved man who mysteriously grows devilish horns in "Horns," by French horror auteur Alexandre Aja.
And he told the London Evening Standard newspaper on Tuesday that two of his dream roles are musical satirist Tom Lehrer and rocker Iggy Pop.
"The Cripple of Inishmaan," which runs to Aug. 31, is part of a West End season of plays overseen by Grandage, who has assembled an A-list company of actors that includes Radcliffe, Ben Whishaw, Judi Dench and Jude Law.