Glen Hansard, a singer-songwriter who was frontman of the popular Irish band the Frames and shared an Oscar for the wistful music he co-wrote for the 2006 Irish independent film “Once,” which subsequently became a Tony Award-winning play, died on Wednesday in a motorcycle crash in Dublin. He was 56.

Mr. Hansard’s representative, ATC Management, confirmed the songwriter’s death on his website.

Micheál Martin, Ireland’s prime minister, known in the country as the taoiseach, wrote on social media: “Deeply saddened to learn of the passing of Glen Hansard. A talented musician and actor who made a significant contribution to Ireland’s cultural landscape over many years.”

The Irish police issued a news release on Wednesday appealing for witnesses to the crash in the Lucan area of West Dublin. The crash occurred shortly before 4:30 a.m., the news release said. It did not name Mr. Hansard but said that “the motorcyclist, a man in his 50s, was treated at the scene but was pronounced deceased a short time later.” On Wednesday, the Irish news media reported that Mr. Hansard was the victim.

Mr. Hansard, who began performing as a busker on the streets of Dublin, formed the Frames in 1990, and the band went on to have multiple hit albums in Ireland. He came to more international fame after starring in “Once,” a movie about an Irish street musician and the woman he falls for. He and his co-star, Marketa Irglova, won a 2008 Academy Award for best song for “Falling Slowly,” which is featured in the film.

A.O. Scott, in a review of “Once” for The New York Times, said it was a simple film about a busker (Mr. Hansard) who meets a Czech pianist (Ms. Irglova) while out on the streets, and the two then become collaborators and potential lovers. “You can’t take your eyes off them,” A.O. Scott said, describing the movie as “almost perfect.”

Mr. Hansard previously had a small role in “The Commitments,” and said in a 2007 interview with The Times that he had been reluctant to act again. “I’m a real believer in sticking to your craft,” he said. He eventually accepted on the stipulation that he could flee if the first few days of filming didn’t work out, he said.

Glen Hansard was born on April 21, 1970, in Dublin and grew up in a working-class household. His father, a heavy drinker, was prone to bouts of violence, the singer said in a 2012 interview with The Times. “My dad was quiet, angry, shut down,” he said, “so my thing is: I express everything that’s there. I want to get it all out.”

When an uncle left a guitar behind after being sent to prison, Mr. Hansard picked up the instrument. “I was kind of in a funny spot. I was getting into trouble,” he said in a recent podcast interview, recalling his journey to learning guitar. He soon fell in love with the music of Bob Dylan, Leonard Cohen and Van Morrison.

He dropped out of school to busk and play in bands. By 1990, he had formed what would be his own longtime rock band, the Frames.

He started acting when he won a role in “The Commitments,” the 1991 film about a group of working-class Irish young people who form a 10-piece soul band. Mr. Hansard said in the podcast interview that he had tagged along with a friend who was auditioning for a role in the film.

“I fit the bill. I had red hair and I played the guitar,” he said of his character, Outspan Foster. “I read a couple of lines, and I got the part.”

The film was positively received, with The Times calling the cast “a group of talented newcomers.”

Then came an even bigger breakout: “Once,” the 2007 Irish film that catapulted Mr. Hansard into international stardom. The wistful film, written and directed by John Carney, one of Mr. Hansard’s former bandmates, was filmed in 17 days on a modest budget. It became a hit at the Sundance Film Festival and went on to inspire a Tony Award-winning musical of the same name.

Mr. Hansard, who initially resisted the idea of turning “Once” into a musical, eventually gave the production his blessing. “Forget about being correct,” he recalled telling Steve Kazee, the actor who played his role in the Broadway production. “The muse hates correct.”

He leaned into being a solo artist in the years after “Once,” releasing albums including 2015’s “Didn’t He Ramble,” which was nominated for a Grammy Award.

Mr. Hansard was also an activist, campaigning for awareness of homelessness and protesting over housing shortages. He performed often in an annual Christmas Eve Busk event in Dublin, an event that raises money to help people at risk of homelessness.

The singer had been scheduled to play European tour dates in the coming months to perform music from two albums released this year. He is survived by his wife, Maire Saaritsa; three brothers; and a son, Christy.

As well as the Frames, Mr. Hansard played with the Swell Season, a folk duo he formed with Ms. Irglova, his “Once” co-star and onetime partner.

Mr. Hansard said in the 2012 Times interview that he always found himself singing “within the vernacular of the love song,” but that his music wasn’t simply about romance.

“It’s also the relationship between me and my country, me and my friends, me and myself, me and my god,” he said. “It’s not always about me and my girl. That’s just the language I’ve gotten used to using.”