Bob Avian, a choreographer, director and producer who was deeply involved in some of the biggest Broadway shows of the last 60 years, including — with his frequent collaborator, Michael Bennett — “A Chorus Line,” one of the longest-running musicals in history, died on Thursday in Fort Lauderdale, Fla. He was 83.

His husband, Peter Pileski, said through a spokesman that the cause was cardiac arrest.

Mr. Avian also choreographed the Broadway hits “Miss Saigon” (1991) and “Sunset Boulevard” (1994), among others, and directed a 2006 revival of “A Chorus Line” that ran on Broadway for almost two years, as well as productions of that show in London in 2013 and at New York City Center in 2018. He shared Tony Awards for choreography with Mr. Bennett for “A Chorus Line” (1975) and “Ballroom” (1978).

It all started with a happenstance of casting. Mr. Avian began his career as a dancer, and early on, about 1960, he was cast in an international tour of “West Side Story.”

“I loved the adventure of traveling around the world,” he wrote in “Dancing Man: A Broadway Choreographer’s Journey,” a memoir written with Tom Santopietro and published last year, “but the tour would prove even more momentous for one all-encompassing reason: During rehearsals in New York, I met a fellow castmate, Michael Bennett, a 17-year-old high school dropout marked for greatness.”

The two became friends, and within a few years Mr. Bennett had graduated from dancer to choreographer. In 1968, when he choreographed the Neil Simon/Burt Bacharach/Hal David musical “Promises, Promises” for Broadway, he brought Mr. Avian aboard as assistant choreographer, and they worked together for the next two decades, until Mr. Bennett’s death from AIDS in 1987.

He was assistant or associate choreographer for Mr. Bennett on “Coco” (1969), “Company” (1970), “Follies” (1971) and “Seesaw” (1973). Then, in 1975, came their biggest hit of all, “A Chorus Line,” on which they were co-choreographers.

“A Chorus Line” is a musical about dancers creating a musical, and with Mr. Bennett’s and Mr. Avian’s snazzy footwork and Marvin Hamlisch’s catchy music, it caused a sensation.

“The conservative word for ‘A Chorus Line’ might be tremendous, or perhaps terrific,” Clive Barnes wrote in The New York Times, reviewing the original production at the Public Theater in May 1975; it quickly moved uptown and ran for 15 years and 6,137 performances on Broadway, a record at the time (though it has since been surpassed by several shows).

Revisiting the show in 2013 in England, Mr. Avian reflected on its appeal.

“The show is about the anonymous kid in the chorus, the guy who works on the assembly line, the clerk in the store,” he told The Telegraph of London. “They are everyone. It’s not bigger than life; it is life.”

In his memoir, Mr. Avian wrote about what made his creative partnership with Mr. Bennett work.

“I wasn’t cautious with Michael,” he wrote. “I knew him so well that I could tell him exactly what I thought. In effect I seemed to instinctively assume the role of his editor. Michael was a more mercurial personality than I, and ambitious though I was, I did not possess Michael’s burning intensity. I didn’t want to be Michael, and he didn’t want to be me.”

Robert Avedisian (he shortened the name when he became a professional dancer) was born on Dec. 26, 1937, in Manhattan to John and Esther (Keleshian) Avedisian, immigrants from Armenia. His father was a chef, and his mother was a seamstress. By the time he was 11, he knew he loved to dance and was pretty good at it.

“When my parents went out, I would push back the furniture, clear an open space, turn on the record player and leap around the apartment,” he wrote in his memoir. “Boys weren’t supposed to dance, especially not in Armenian culture, but I loved music, and I especially loved the freedom I found in dancing.”

He didn’t have any formal training, though, until he enrolled at Boston University, where he graduated from the College of Fine Arts in 1958. He also studied at the Boston Ballet School.

After the “West Side Story” tour — which was playing Berlin when the Berlin Wall went up in 1961 — he booked a national tour of “Carnival!,” working under the director and choreographer Gower Champion. Not long after, he got his first chance to see a show choreographed by his friend Mr. Bennett, a summer stock production of the Richard Rodgers musical “No Strings.”

“I knew right away that he had it — and he knew he had it,” Mr. Avian wrote.

Mr. Bennett’s career took off, and with it Mr. Avian’s soon did too.

Some of their projects were more challenging than others. There was, for instance, “Coco,” a 1969 André Previn-Alan Jay Lerner musical that garnered a lot of attention, both for its enormous budget and for its star, Katharine Hepburn, who played the fashion designer Coco Chanel. Mr. Bennett was the choreographer, Mr. Avian his assistant, and from the beginning they realized that they had their work cut out for them. Mr. Avian recounted the first rehearsal in “Dancing Man”:

“We’re excited and even in awe of the great Kate — for precisely 10 minutes. And then Michael and I look at each other and realize there’s an elephant in the room: The legendary Katharine Hepburn doesn’t have a musical bone in her body.”

Still, though critics were unkind, “Coco” ran for 329 performances on the basis of star power alone.

Mr. Avian wasn’t limited to the choreographic side of things in his work with Mr. Bennett. On “Ballroom,” in addition to his Tony-winning choreography, he was a producer. And on their next collaboration, “Dreamgirls” (1981), which Mr. Bennett directed and choreographed, he was a lead producer. That show ran on Broadway for more than three and a half years.

When Mr. Bennett became ill, Mr. Avian wasn’t sure about his own future, and particularly about whether to accept an offer from the producer Cameron Mackintosh to stage a revival of “Follies” in 1987. In an interview with The New York Post last year, he said it had been Mr. Bennett, near death at the time, who spurred him on, telling him: “You should do this. You know what we did with the original, and you know the characters.”

Mr. Avian went on to do the “musical staging” (as the credit reads) for Mr. Mackintosh’s production of “Miss Saigon,” for Andrew Lloyd Webber’s “Sunset Boulevard” and, in 1999, for the Stephen Sondheim revue “Putting It Together.”

Mr. Avian and Mr. Pileski, who had been together for 36 years and had homes in Fort Lauderdale, New York and Connecticut, married in 2011. He is also survived by a sister, Laura Nabedian.