His daughter, Madeline Stuart, said he died Thursday night of cancer at his home in Los Angeles.
Stuart's documentaries include "The Making of the President 1960," for which he won an Emmy, as well as subsequent explorations of the 1964 and '68 campaigns. Other programs were "The Rise and Fall of the Third Reich" and the Oscar-nominated "Four Days in November."
His groundbreaking 1973 film "Wattstax" focused on the Wattstax music festival of the previous year and Los Angeles' Watts community in the aftermath of the 1965 riots.
But while Stuart's documentaries won acclaim and cemented his reputation, he won a special sort of following with the 1971 musical fantasy "Willy Wonka."
That film was his response to a young reader of the Roald Dahl children's classic "Charlie and the Chocolate Factory": Stuart's daughter Madeline asked her dad to make a movie of the book she loved. Starring Wilder as Willy Wonka (and with 11-year-old Madeline in a cameo role as a student in a classroom scene), it became an enduring family favorite.
A collaborator on "Willy Wonka" was screenwriter David Seltzer, who at 26 had gotten his first job in the film business - making documentaries - from Stuart and calls him "a mentor by way of drill sergeant, much-feared boss and much-loved friend."
Seltzer, who also wrote "The Omen" and last year's HBO film "Cinema Verite," said Friday that Stuart dismissed his first effort at a screenplay "with the scolding that if I didn't 'have a drawer-full of magic,' I had no business even thinking I was a screenwriter. He taught me that good enough wasn't good enough."
During the 1960s and 1970s, Stuart was associated with David L. Wolper, with whom he established a base of West Coast documentary production at a time when New York filmmakers and TV networks' news divisions dominated the field.
By 1980, Stuart was an independent producer and director whose credits include portraits for PBS' "American Masters" on artist Man Ray and the director Billy Wilder. He was executive producer of the 1980s ABC series "Ripley's Believe It or Not," whose host was Jack Palance.
Airing on PBS in 2005, "The Hobart Shakespeareans" was Stuart's profile of a teacher in inner-city Los Angeles whose fifth-grade class each year performed a play by William Shakespeare.
He produced or directed various dramas including "The Triangle Factory Fire Scandal," ''Ruby and Oswald" and the 1981 TV film "Bill," starring Mickey Rooney and Dennis Quaid, which won a Golden Globe and a Peabody award.
Besides "Willy Wonka," Stuart's theatrical features include the 1969 comedy-romance, "If It's Tuesday, This Must Be Belgium," starring Suzanne Pleshette and Ian McShane, and, a year later, "I Love My Wife," with Elliott Gould.
A New York native, Stuart attended New York University, where he set aside his early aspirations to be a composer in favor of a career in filmmaking.
Before joining forces with the Wolper Organization, he was a researcher for CBS News' 1950s documentary series, "The 20th Century," which was hosted and narrated by Walter Cronkite.
Besides his daughter, an interior designer, Stuart is survived by sons Andrew, a literary agent, and Peter, a filmmaker.