Rod McKuen in 1973. He was a hugely popular poet, singer and songwriter in the 1960s and 1970s. (Arthur Ellis/The Washington Post)

Rod McKuen, a California writer, singer and troubadour whose books of poetry and understated record albums sold by the millions in the 1960s and 1970s, making him the best-known and most vilified poets of the 20th century, died Jan. 29 at a rehabilitation facility in Beverly Hills, Calif. He was 81.

His half brother and longtime manager, Edward McKuen Habib, confirmed the death to news outlets. The cause was pneumonia.

At the height of his fame, Mr. McKuen seemed to embody a sensibility of earnest, inward-looking wistfulness often associated with the 1960s. Many of his books became bestsellers, and his songs were featured in film scores and in hundreds of recordings.

Lanky and casually attired, he became a familiar figure on television as he delivered his lyrics in a raspy voice that barely rose above a whisper.

Critics had a field day tearing apart Mr. McKuen’s work, mocking him as the “king of kitsch,” whose simple versifying made greeting cards read like T.S. Eliot.

Even if his writing was banal, the public remained enthralled with Mr. McKuen and his seemingly endless body of work for more than a decade. He won a Grammy Award in 1969 for best spoken-word recording and was nominated for an Academy Award in 1970 for “Jean,” a hit song from the film “The Prime of Miss Jean Brodie.”

His books of poetry, which eventually numbered more than 30, were instant bestsellers, and he released an estimated 200 record albums. He sold more than 60 million copies of his books and more than 100 million musical recordings.

He wrote 1,500 songs, which were recorded by artists as diverse as Johnny Cash, Barbra Streisand, Perry Como, Petula Clark and Madonna. Frank Sinatra’s 1969 album of Mr. McKuen’s music, “A Man Alone,” was the only time the singer devoted an entire record to one composer.

Mr. McKuen lived in Paris for a time in the 1960s, and he became something of an English-language version of the French chansonnier, or a combination of songwriter, singer and bard.

He was a close friend of the Belgian-born Jacques Brel, with whom he collaborated on musical projects, including one of Mr. McKuen’s most enduring songs, “If You Go Away,” which was a translation of Brel’s “Ne Me Quitte Pas.” Mr. McKuen’s “Seasons in the Sun,” a top-selling single for Terry Jacks in 1974, was based on another Brel composition.

In the late 1960s, Mr. McKuen became a sudden, almost unexplainable phenomenon. Folk singer Glenn Yarbrough recorded his songs in the 1967 album “The Lonely Things,” prompting fans to ask where the lyrics came from. Mr. McKuen said they were drawn from his book of poetry called “Stanyan Street and Other Sorrows” — only the book did not exist.

He hurriedly wrote the poems in two weeks, and “Stanyan Street” became one of Mr. McKuen’s first bestsellers.

A 1967 Time magazine article characterized his poetry as nothing but “sweet love, lonely rooms, silent rain, quiet snow, and lost cats.” A Newsweek critic called him the “king of kitsch.”

Poet Karl Shapiro was even more dismissive. “It is irrelevant to speak of McKuen as a poet,” he wrote in 1968. “His poetry is not even trash.”

But Mr. McKuen, a seasoned disc jockey, singer, actor and coffeehouse poet, was as much a performer as a writer. A poem such as “A Cat Named Sloopy” — in which he coined the phrase “midnight cowboy” — might look silly on the page, but he had a way of delivering the lines in a surprisingly affecting manner:

Once was a time,

in New York’s jungle in a tree,

before I went into the world

in search of other kinds of love

nobody owned me but a cat named Sloopy.

Looking back

perhaps she’s been

the only human thing

that ever gave back love to me.

Rodney Marvin McKuen was born April 29, 1933, at a Salvation Army charity hospital in Oakland, Calif. His father had already deserted his mother, who worked as a waitress, telephone operator and, briefly, a dance-hall hostess.

Mr. McKuen received such severe beatings from his alcoholic stepfather, he said, that he was sometimes left with broken arms and ribs. In 1982, Mr. McKuen revealed that he had been sexually abused by an uncle and an aunt when he was 7.

With only four years of schooling, Mr. McKuen said he ran away from home when he was 11. He drifted throughout the West, finding work in a Nabisco factory and as a cowboy, lumberjack and gravedigger.

By the time he was 15, he was a disc jockey for a San Francisco-area radio station, playing records and dispensing lonely-hearts advice to late-night callers. He wrote a newspaper entertainment column and acted in plays before serving with the Army in Asia during the Korean War.

Back in San Francisco, he worked as a jazz and ballad singer and spent several months touring with Lionel Hampton’s band. He began to read his poetry at coffeehouses with Jack Kerouac and Allen Ginsberg.

For two years in the late 1950s, Mr. McKuen was a contract actor for Universal, appearing in several minor TV and film roles.

After moving to New York in 1959, he survived by selling blood before landing a job writing music for CBS. He also sang in a rock band and wrote a minor hit in 1961, “Mister Oliver Twist,” capitalizing on the twist, a popular dance craze of the time.

On tour, Mr. McKuen damaged his vocal cords, and his once-smooth tenor became, in his words, “the sort of voice that makes the people in the audience want to clear their throats.”

By the late 1960s, he was one of the country’s most popular entertainers in any field. He celebrated his 36th birthday in 1969 with a sold-out show at New York’s Carnegie Hall.

“His voice, to use the term loosely,” New York Times critic Robert Sherman wrote about that performance, “ranges from a smoky purr down to a strangulated whisper, yet it has undeniable warmth and a virile intimacy that seems to reach out and stroke the audience into willing submission.”

Mr. McKuen, who seldom slept more than five hours a night, performed as many as 300 concerts a year. He composed some classical works and wrote music for various Hollywood projects, including the animated feature “A Boy Named Charlie Brown” (1969) and the 1973 TV movie “Lisa, Bright and Dark.”

Meanwhile, he poured out one best-selling poetry volume after another, such as “Lonesome Cities” (1968), “The World of Rod McKuen” (1968) and “Celebrations of the Heart” (1975).

Although his writing was seldom overtly political, Mr. McKuen was nevertheless an opponent of the Vietnam War, an early supporter of gay rights and an advocate of children’s rights. In South Africa in 1977, he was reportedly the first entertainer to demand that the audience be integrated.

Mr. McKuen stopped performing in 1981, later revealing that he was suffering from clinical depression. He continued to write books, but he largely stayed out of the public eye.

When he attempted a comeback in 2001, he found that his fame had ebbed away, and he was unknown to a younger generation. He occasionally performed in small venues until he was almost 80, singing a mix of classic standards and his hits from decades past.

In 1976, he published a memoir, “Finding My Father: One Man’s Search for Identity,” in which he tried to trace the identity of his biological father. He concluded that his father was a onetime lumberjack who ended up delivering ice in California, 20 miles from Mr. McKuen’s home in Beverly Hills.

Always vague when asked about his romantic attachments, Mr. McKuen never married. He was the father of two children, who grew up in Paris with their French mother.

Before he became well known, Mr. McKuen said, his books usually received laudatory reviews. Only after he became famous, and his music and words sold in the millions, did the reviews turn more critical and even nasty.

He was at a loss to explain why.

“The most unforgivable sin in the world,” Mr. McKuen told The Washington Post in 1969, “is to be a best-selling poet.”