NEW YORK — In Central Park’s Strawberry Fields, John Lennon lives forever.

A small but ardent collection of fans both old and new came together Tuesday to mark the 40th anniversary of Lennon’s murder, gathering in the stretch of Central Park named for one of his Beatles classics to play guitars, sing and remember the rock star now dead as long as he lived.

“The Beatles music is forever,” said Jamie Battan, a Manhattan resident in his 60s. “It’s the best music, in my opinion.”

Lennon, 40, was gunned down by a crazed fan just outside his Upper West Side home — a short walk from Strawberry Fields, where half a dozen fans with guitars sat on benches to play his songs. The centerpiece of the memorial, opened Oct. 9, 1985, on Lennon’s 45th birthday, remains an elaborate mosaic bearing a single word: “Imagine.”

Lennon’s fans were joined by his fellow former Beatles, songwriting partner Paul McCartney and drummer Ringo Starr, in remembering the slain star.

“A very very sad day but remembering my friend John with the great joy he brought to the world,” wrote McCartney on Twitter.

Starr, along with a vintage photo of the two sitting on a car bumper, tweeted a request to honor his old friend: “Peace and love John. I’m asking Every music radio station in the world sometime today play Strawberry Fields Forever.”

Lennon’s widow, Yoko Ono, who once urged the world to “give peace a chance” alongside her husband, noted in a tweet that “over 1,436,000 people have been killed by guns in the U.S.A. since John Lennon was shot and killed on Dec. 8, 1980.”

In years past, a few of the devotees recalled, the fans were joined by Lennon’s oldest son, Julian, and fellow Rock & Roll Hall of Fame musician Rod Stewart for the annual Dec. 8 get-together. The hardcore fans arriving throughout the day left roses, candles and photos of Lennon on the mosaic to mark the sad anniversary on a cold December day.

“I was a young teenager when (the Beatles) became popular,” said Katie Cangelosi, 70, a regular visitor each year. “It’s been a continuous presence in my life, starting out as such a huge fan. John Lennon has been a force for good.”

Cangelosi took a seat on a park bench and listened to the musicians paying homage to the working class hero: “It’s a good time to sort of sit and contemplate.”

Guitarist Tepper Saffren, 28, wore a Lennon-esque outfit of tinted glasses with round frames and a beanie as he prepared to play some of the Liverpool native’s songs.

“I think that what he represents is sort of this fight for goodness,” said the musician, who performs under the name “Sgt. Tepper.”

“This idea that we can choose a good life,” said the young guitarist, born 12 years after Lennon’s death. “Spreading love, spreading kindness, curiosity and trust. That’s sort of been a life goal of mine.”

Irene Toscano, 28, grew up in Lennon’s old Upper West Side neighborhood and typically shows up every Dec. 8.

“It’s his message of peace and love and bringing people together, regardless of religion, where you’re from, who you are, the color of your skin,” she said. “It still resonates today. And unfortunately, we’re not there yet, although we are working on it.”