Neil Simon, one of the rare late-20th century playwrights who was a brand name for plays such as “The Odd Couple” and “Barefoot in the Park,” died Sunday. He was 91.

A statement from his reps said, “Neil Simon, the Pulitzer Prize-winning American playwright, died last night at New York-Presbyterian Hospital in New York City. The cause was complications from pneumonia.”

“His wife, Elaine Joyce Simon, was at his bedside along with Mr. Simon’s daughters, Ellen Simon and Nancy Simon.”

In addition to his four Oscar nominations and 17 Tony nominations, Simon’s works brought an unsurpassed 50 Tony nominations for their actors. His competitive Tony wins came for “The Odd Couple” (best playwright) and for best play for “Lost in Yonkers” and “Biloxi Blues.”

Beginning in the 1960s, Simon could guarantee good Broadway advance sales, a rare feat for a writer. He had more than 30 plays mounted on Broadway, including four that ran simultaneously in 1966: “Sweet Charity,” “The Star-Spangled Girl,” “The Odd Couple” and “Barefoot in the Park.”

He also wrote numerous screenplays, some of them originals, some adaptations of his stage work. But he was best known as a playwright, both for his long string of Gotham shows as well as countless productions by regional and amateur theater companies, which helped him become the most-performed playwright of his era.

At a time when the legitimate theater was in decline and devoted American playwrights an endangered species, Simon stood head and shoulders above the rest. His early comedic successes, such as “The Odd Couple” and “Barefoot in the Park,” were both critically well received and financially successful, and even some critics who found him glib and formulaic could not deny his craftsmanship and the sheer volume of his output.

Simon once said that he was a disciplined writer, sitting at a typewriter for eight hours and constantly banging on the keys even if he was writing gibberish, because he needed the regularity of constantly writing.

After decades of writing comedies, he began to win more awards with his more introspective and autobiographical plays, exploring his working-class upbringing in such comedy-dramas as “Brighton Beach Memoirs” and the Tony and Pulitzer winner “Lost in Yonkers.”

Simon never much wandered from his roots. And even when his plays were geographically distant from his New York-Jewish background, the sensibility remained in the approach to comedy and the characters that inhabited his pieces. A Neil Simon comedy was as identifiable as the work of any other major American playwright, whether O’Neill, Williams or Philip Barry.

In addition to his screen adaptations of plays, he wrote original motion picture scripts including “The Goodbye Girl,” the 1972 “The Heartbreak Kid” (adapted from Bruce Jay Friedman’s story) and 1976’s “Murder by Death.” But he maintained a fervor and enthusiasm for the theater that made him unique in the era of television and film.

Simon got his start in TV, as one of the writers on “Your Show of Shows,” the landmark comedic variety show of the 1950s that starred Sid Caesar and Imogene Coca. His colleagues included Carl Reiner, Larry Gelbart and Mel Brooks.

Marvin Neil Simon was born on the Fourth of July, in the Bronx. He was dubbed Doc as a young boy — he had a habit of imitating the family doctor — and it stuck, long after people forgot his original first name, Marvin.

He and older brother Danny first began writing comedy skits when Doc was only 15. After a stint in the Army, he and Danny were reunited at Warner Bros. Danny was working in publicity and his brother in the mailroom. Simon got his BA from NYU in 1946.

Their work impressed CBS producer Goodman Ace, and he hired them to script a radio show for Robert Q. Lewis. After writing material for Phil Silvers, Jackie Gleason and Jerry Lester, Simon landed on “Your Show of Shows” as well as Phil Silvers’ shows, including the weekly comedy “Sgt. Bilko.” Simon also wrote material for Tallulah Bankhead’s 1951 show and “The Garry Moore Show.”

Tiring of the sausage factory atmosphere of collaborative TV writing, Simon struck out on his own after writing and rewriting the play “Come Blow Your Horn” about 15 times. It landed on Broadway and became his first success in 1961, earning him $1,000 a week and freedom from television.

Simon then penned the book for the Sid Caesar-starring musical “Little Me” in 1962, followed by his first major success, “Barefoot in the Park,” in 1963. The comedy became one of Broadway’s longest-running legitimate plays, with 1,532 performances, and a smash film in 1967. His next comedy, 1965’s “The Odd Couple,” would top even that success, especially as a film and a long-running TV sitcom (though Simon had no connection to the TV series); the play was revived on Broadway in 1985 with a gender switch and again in 2005. Key to Simon’s early successes was his director, Mike Nichols.

His output during the 1960s included two musical librettos, “Sweet Charity” and “Promises, Promises,” based on Federico Fellini’s “Nights of Cabiria” and Billy Wilder’s “The Apartment,” respectively. “The Star-Spangled Girl” was an attempt to break from his roots. “Plaza Suite” was a bigger hit, a trio of one-acts set in the Plaza Hotel. He would return to the format for “California Suite” and “London Suite.”

His 1969 comedy hit “The Last of the Red Hot Lovers,” about a man and the women in his life, would also set the format for 1990’s “Jake’s Women,” a play that failed to make it to Broadway. “The Gingerbread Lady” (1970) was his first attempt at more serious dramatic fare, and with less spectacular results. In the early ’70s he sought to emulate Chekov with “The Good Doctor,” and he wrote a biblical parable, “God’s Favorite.”

Audiences clamored for his more commercial fare such as “The Prisoner of Second Avenue,” “California Suite” and “The Sunshine Boys.” “Sunshine Boys,” which was an even bigger success onscreen, was written while his wife of 20 years, Joan, was dying of cancer. She was the mother of his daughters Ellen and Nancy, and the emotional devastation of that life passage and his rapid turnaround marriage to actress Marsha Mason formed the basis of his first serious-minded success, “Chapter Two,” in 1977.

Even before he began adapting his plays to the screen, Simon had written the feature comedy “After the Fox” in 1966. His first original bigscreen comedy to become a hit was “The Out-of-Towners,” which starred Jack Lemmon and Sandy Dennis.

The detective spoof “Murder by Death” followed, and his 1977 “The Goodbye Girl” won an Oscar for Richard Dreyfuss and brought wife Mason a nomination.

Simon’s screen career was fostered by producer Ray Stark, who shepherded many of the playwright’s stage comedies and original works to the screen.

Simon had won a Tony for “The Odd Couple” in 1965, several of his plays and musicals had been Tony nominated, and he was worth more than $10 million, but the ease of his popular appeal worked against him critically. The turnaround began with “Brighton Beach Memoirs” in 1983. The autobiographical drama of his adolescence brought Simon his first taste of serious acclaim. It was followed by the more comedic but equally pungent “Biloxi Blues,” a coming-of age-comedy about his uneventful Army days. Like “Brighton Beach,” it starred Matthew Broderick as Eugene, Simon’s alter ego. And it won Simon another Tony for best play in 1985. The trilogy was completed with “Broadway Bound,” about his early career in the theater.

In 1991 his play “Lost in Yonkers,” another serio-comedy, brought him his highest accolade — a Pulitzer Prize for drama — as well as a third Tony award.

After the film version of “Biloxi Blues,” his movies failed to ignite. Similarly, such plays as “Jake’s Women” were a miss, and “Rumors” and “Laughter on the 23rd Floor,” about his TV comedy writing days, falled to catch on.

But by then Simon was the most popular and frequently performed playwright of his day. His 1997 autobiography “The Play Goes On: A Memoir” was a success.

Simon penned an original screenplay sequel to “The Odd Couple.” The 1998 film reunited the stars reunited the stars of the original film, Walter Matthau and Jack Lemmon; Matthau had created the role of Oscar Madison on Broadway.

Simon’s most recent new works to play Broadway received generally mixed notices, with critics finding 2000 offering “The Dinner Party” an intriguing but unsuccessful detour into darker territory and 2001 play “45 Seconds from Broadway” considered sweet-natured but slim.

The past few decades saw TV remakes of “The Sunshine Boys,” “Plaza Suite,” “The Goodbye Girl” as well as bigscreen remakes of “The Heartbreak Kid” and “The Out of Towners,” while Broadway revived “Sweet Charity,” “The Odd Couple,” “Barefoot in the Park,” “Brighton Beach Memoirs” and “Promises, Promises.”

In 2006 he won the Mark Twain Prize for Humor, presented by the Kennedy Center; he had also received a special Tony for contributions to the theater in 1975.

Simon married five times. He is survived by his wife, actress Elaine Joyce; three daughters; three grandchildren and one great-grandson.

(Gordon Cox contributed to this report.)