Rooney's son Michael Joseph Rooney confirmed the actor's death to New York Times. The celebrity website TMZ said that Rooney had been ill for some time and died of natural causes.
Rooney rose to fame alongside Judy Garland as the plucky diminutive lad — he was 1.6 meters tall — was in the successful "Andy Hardy" film series of the late 1930s and early 1940s.
He also had notable turns as Puck in "A Midsummer Night's Dream" (1935) and in "National Velvet" (1944), opposite fellow child actor, 13-year-old Elizabeth Taylor.
More recently the still energetic Rooney appeared in the 2006 comedy "Night at the Museum," and in the 2011 movie "The Muppets."
Credited with performances in more than 200 films, Rooney was awarded an honorary Oscar in 1982 for lifetime achievement.
While professionally successful, Rooney had a rocky personal life. He made and lost millions of dollars, married eight times and legally separated from his last wife, Jan, in June 2012.
Along the way he fathered nine children.
The son of vaudeville performers who divorced when he was three, Rooney was born Joe Yule Junior on September 23, 1920 in Brooklyn, New York.
He went on the road with his parents' act at just two weeks old and accidentally became part of the act at 17 months.
Legend has it that a spotlight found the infant crouching underneath a shoeshine stand in the theater where his father was performing after he sneezed and blew his father's cover.
Startled, the toddler stood up and blew into a toy instrument attached to a string around his neck, and peals of laughter broke out in the audience.
Rooney made his big screen debut a few years later, in the 1926 film "Not to Be Trusted," and from 1927 to 1933, he went on to make about 50 silent comedies playing the comic-strip character Mickey McGuire.
Later, after meeting Judy Garland at an acting class, he appeared with the popular young actress in a string of successful films, including the "Andy Hardy" series starting at age 17.
Rooney was what in Hollywood is called a "triple threat" - he could act, sing and dance, all with amazing aplomb.
"The audience and I are friends," Rooney once said. "They allowed me to grow up with them. I've let them down several times, they've let me down several times. But we're all family."
Rooney was the number-one US box office draw between 1939 and 1941, besting big names like Clark Gable and Spencer Tracy. He even won a special youth Oscar in 1939.
But Rooney was drafted during World War II — he served in a morale-boosting entertainment unit — and found it difficult to relaunch his career when he returned to Hollywood.
He re-invented himself as a character actor, picking up small roles, and eventually landed his own television show, "The Mickey Rooney Show," in 1954.
In the 1960s, he made the rounds of nightclubs and the theater circuit while he continued to play secondary roles in movies like "Breakfast at Tiffany's" (1961) and "It's a Mad, Mad, Mad, Mad World" (1963).
He also shined as a horse trainer in the 1979 movie "The Black Stallion" — for which he received an Oscar nomination for best supporting actor — and later in the 1990-1993 TV series "The New Adventures of the Black Stallion."
Aside from the film and TV roles, in the 1970s he took to the stage, and nominated for a Tony Award for best actor in 1980 for his Broadway role in the hit show "Sugar Babies".
Speaking in an interview once about his multiple marriages, which included a trip down the aisle with sultry Hollywood legend Ava Gardner, Rooney quipped: "When I say 'I do,' the Justice of the Peace replies, 'I know, I know.' I'm the only man in the world whose marriage license reads, 'To Whom It May Concern.'"
"I had bad luck in marriage," Rooney said in a 2003 interview with a Florida newspaper, "but I'm grateful that they left me with seven sons and four daughters and seven grandchildren."
His final wife, Jan Chamberlin Rooney, told the Florida paper she "didn't want to marry him because of his track record, but I really fell in love with him. We've been married 30 years, and it's the ups that count."
That fairy tale marriage however also ended in acrimony when the couple separated in 2012.
In 2011, he filed elder abuse and fraud charges against stepson Christopher Aber, the son of his last wife, and Aber's wife. A court issued a restraining order against the Abers, and the case was settled in 2013 in Rooney's favor.
And yet Rooney continued to act: he is set to appear in the upcoming third installment of the Ben Stiller "Night at the Museum" comedy series.
"Had the honor of shooting w MickeyRooney on NATM3 just last month," wrote producer Shawn Levy on Twitter. "A legend, obviously, but something more: grateful, gracious, vital & warm."