A tall Midwesterner with a soaring tenor voice, Mr. Creel won over audiences from his first appearance on Broadway, opposite Sutton Foster in the 2002 musical “Thoroughly Modern Millie.” Set in Jazz Age New York and adapted from a 1967 movie of the same name, the show brought him a Tony nomination for best actor — he played Jimmy Smith, Foster’s playful love interest — and established him as one of musical theater’s most talented young performers.

Mr. Creel went on to star as clean-cut innocents and comically conceited young men, toggling between productions in New York and on London’s West End, where he debuted in 2006 as Bert in “Mary Poppins.”

He received a second Tony nomination in 2009, showing a scruffier side as the hippie Claude in a revival of “Hair,” and won the Olivier for best actor in a musical in 2014, starring in “The Book of Mormon” as Elder Price, an egotistical missionary dispatched to a Ugandan village.

Three years later, he appeared in an all-star revival of “Hello, Dolly!,” winning the Tony for his supporting role as the effervescent clerk Cornelius Hackl. The musical opened in April 2017 and ran for 16 months, with a cast that included Bette Midler, Donna Murphy, Bernadette Peters and two of Mr. Creel’s “mentors and heroes”: Victor Garber and David Hyde Pierce, who played his character’s wealthy boss.

“That show wasn’t a musical. It was an event,” Mr. Creel told the San Francisco Chronicle in 2018. He added, “I tried to play it cool, act like it made sense, but it didn’t make any sense.”

Mr. Creel, who also won a Drama Desk Award for the role, was unusually candid about his life as an actor and the divide he sometimes felt between his private self and the beaming, ever-cheery version he often presented to the public.

“I can be blissfully happy,” he told Metrosource magazine last year, “and also deeply anxious and severely lonely.” A statement from his publicist noted that Mr. Creel had the word “both” tattooed on his left wrist, as a reminder of life’s “inherent contradictions.”

At times Mr. Creel drew on those contradictions for his work, finding connections between his life and the characters he played, even when his roles were ripped straight out of storybooks.

For his last Broadway musical, the 2022 revival of Stephen Sondheim’s fractured fairy-tale showcase “Into the Woods,” he starred as the Wolf as well as Cinderella’s Prince, delivering a performance that New York Times reviewer Alexis Soloski hailed as “sleazy and flawless.”

Mr. Creel told Metrosource that he played the Prince as someone who was fundamentally insecure and identified with the role as a gay man who publicly came out in his early 30s while preparing for his third Broadway musical. For years, he said, he “was constantly trying to please everybody and get things that made people see I was worthy, when I actually didn’t really think I was worthy at all.

“I was just a shame-filled, sad, homophobic, self-loathing, homosexual for so long, you know?” he continued. “And I thought, oh, I know him. That guy’s insecure and scared. He is trying to puff up and show everybody that he’s a king when actually he feels like he’s a coward. Until he can face his cowardice, he can’t be a king.”

The youngest of three children, Gavin James Creel was born in Findlay, Ohio, on April 18, 1976. His mother, the former Nancy Clemens, was an interior decorator; his father, James, worked for Marathon Oil. His grandmother, a music teacher, would play the piano while he sang along as a boy.

Within a few years, Mr. Creel was performing onstage, soloing in “Gary, Indiana” for an elementary school production of “The Music Man.” He took piano and trumpet lessons, sang in the choir at his family’s United Methodist Church and studied musical theater at the University of Michigan, receiving a bachelor’s degree in 1998.

That same year, he appeared in a national touring production of the musical “Fame,” based on a 1980 movie about students at the High School of Performing Arts in New York. He soon made his way to New York, performing in Broadway musicals that included revivals of “La Cage aux Folles” in 2004 and “She Loves Me” opposite Jane Krakowski in 2016.

Mr. Creel also joined the Broadway casts of “The Book of Mormon,” reprising his missionary role after playing Elder Price in London, and appeared in the London and New York productions of “Waitress,” performing on the West End in 2020 alongside the musical’s lyricist and composer, Sara Bareilles.

After he publicly came out as gay during the lead-up to “Hair,” Mr. Creel became an increasingly outspoken advocate for marriage equality, co-founding a grassroots organization, Broadway Impact, to marshal support for same-sex marriage. While performing in the musical, he successfully called on “Hair’s” producers to cancel a performance so that the cast could participate in the 2009 National Equality March, a Washington rally for LGBTQ+ rights.

In addition to his partner, Ward, an actor and singer, survivors include his parents and two sisters.

Away from Broadway, Mr. Creel occasionally acted on-screen, playing a hotel waiter in the 2003 TV movie “Eloise at the Plaza,” starring Julie Andrews, and appearing in a 2021 installment of “American Horror Stories.” He also wrote and performed his own music, putting out three independently released pop albums and singing in concert.

His final credits included an off-Broadway show, “Walk on Through: Confessions of a Museum Novice,” that he wrote and starred in himself, inspired by visits to the Metropolitan Museum of Art. The musical, which closed in January after a two-month run at MCC Theater, received mixed reviews, although critics including Charles Isherwood of the Wall Street Journal admired Mr. Creel’s mischievous lyrics.

For one song, Mr. Creel sang about feeling unmoored — “I wanna be an actor, a doctor, an architect / Or start a sect or new regime” — while standing in front of a Jackson Pollock painting. “The song then transforms into a duet with Pollock, sung by Ryan Vasquez,” Isherwood notes. “Pollock has a dry sense of humor: ‘Have you read my Wikipedia page? Don’t drink and drive.’ ”