'Dennis the Menace' Actor Jay North Dead at 73

Jay North -- a veteran actor who played the eponymous character in the 1960s sitcom "Dennis the Menace" -- has died ... TMZ has confirmed.

Laurie Jacobson -- a longtime friend of North and wife to "Lassie" actor Jon Provost -- tells TMZ ... Jay passed away Sunday at his home in Lake Butler, Florida after a battle with colorectal cancer.

We're told his health started to deteriorate over the past month, and he was surrounded by family -- his wife Cindy and her daughters from a previous marriage, which we're told he "adored" -- when he passed.

Laurie says Cindy and her daughters "gave him a family he never had" since he was an only child who never knew his father.

We're told Jay hadn't seen his friends in some time because he needed to isolate in order to stay healthy due to his cancer ... but, Laurie collected hundreds of letters from fans and gave them to him over Christmas -- which she says he was thrilled about.

North rose to prominence during the late 1950s ... appearing in bit parts on programs like "77 Sunset Strip," "Rescue 8," and "Sugarfoot" when he was less than 10 years old.

Jay gained national recognition in 1959 when he started playing Dennis Mitchell on "Dennis the Menace" ... starring in all 146 episodes from 1959 to 1963. His hair was bleached platinum blonde for the part, and he was instructed to claim he was a year younger than he was in interviews.

North opened up about his struggles on set years after the show ended ... claiming his aunt verbally and physically abused him when he messed up -- even taking him away from prying eyes to beat him when he flubbed a line. He always made it clear his mother and others on set weren't aware of the abuse at the time.

Jacobson adds, "He had a rough ride in Hollywood-- he did not enjoy the experience -- he was at a time very angry and bitter that the adults that surrounded him did nothing to help him or make his time easier."

"Dennis the Menace" was canceled after four seasons ... and, North transitioned to voice acting work in the late 1960s, early '70s on projects like "Arabian Knights," "Here Comes the Grump" and "The Pebbles and Bamm-Bamm Show."

By the late 1980s, North left acting behind ... making limited cameos as himself in the years since on an episode of "The Simpsons" and in the David Spade movie "Dickie Roberts: Former Child Star."

In more recent years, North worked as a correctional officer in Florida ... reportedly helping troubled youth in the juvenile system. He also helped counsel former child stars via the group A Minor Consideration through the 1990s.

Jacobson tells us he also worked with inmates on death row who had troubled childhoods as well ... and their conversations helped him find peace with the early years of his life.

Despite his distaste for Hollywood, Jacobson says Jay did appreciate one perk he got from the industry -- lifelong friends who were also child stars around the same time including Angela Cartwright, Jerry Mathers, Stan Livingston, Paul Petersen and Brandon Cruz, among others.

Jay was 73.