Riefenstahl died in her sleep at home Monday night, her companion, Horst Kettner told the on-line service for the German personality magazine Bunte.
"Her heart simply stopped," Kettner said.
A tireless innovator of film and photographic techniques, Riefenstahl's career centered on a quest for adventure and for portraying physical beauty.
Even as she turned 100 on Aug. 22, 2002, she was strapping on scuba gear to photograph sharks in turquoise waters, although she had begun to complain that injuries sustained in accidents over the years had taken their toll and caused her constant pain.
Despite critical acclaim for her later photographs of the African Nuba people and of undersea flora and fauna, she spent more than half her life trying to live down the films she made for Hitler and for having admired the tyrant who devastated Europe and all but eliminated its Jews.
Even as late as 2002, Riefenstahl was investigated for Holocaust denial after she said she did not know that Gypsies taken from concentration camps to be used as extras in one of her wartime films later died in the camps. Authorities eventually dropped the case, saying her comments did not rise to a prosecutable level.
Speaking to The Associated Press just before her 100th birthday, Riefenstahl dramatically said she has "apologized for ever being born" but that she should not be criticized for her masterful films.
"I don't know what I should apologize for," she said. "I cannot apologize, for example, for having made the film "Triumph of the Will" — it won the top prize. All my films won prizes."
Biographer Juergen Trimborn, who wrote "Riefenstahl: A German Career," said Riefenstahl could not apologize because the Nazi films were the centerpieces of her career.
"One can't speak about Leni Riefenstahl without looking at her entire career in the Third Reich," Trimborn said. "Her most important films were made during the Third Reich — 'Triumph of the Will,' 'Olympia,' — that's what's she's known for."
"Olympia" -- her Fuehrer's eye view of the 1936 Berlin Olympics was a visual poem to the Arayan form, albeit compromised in the Nazi view by American Jesse Owen's winning the hundred meters dash, reports CBS News Correspondent Mark Phillips.
But did her work make her a Nazi? And did it make her -- as many insist -- Hitler's mistress? She always denied both allegations, including to CBS' Dan Rather in a 1980 interview.
"You were not Hitler's pin up?" he asked.
"Oh, no," she replied.
"Or his mistress?" Rather continued.
"Not one day. Not one minute."
Riefenstahl said she had always been guided by the search for beauty, whether it was found in her hypnotizing images of the 1934 Nuremberg rallies with thousands of goose-stepping soldiers and enraptured civilians fawning for their Fuehrer, in her dazzling portrayal of Olympic athletes, or in her still photographs of the sculpted Nuba men.
"I always see more of the good and the beautiful than the ugly and sick," Riefenstahl said. "Through my optimism I naturally prefer and capture the beauty in life."
Born Helene Bertha Amalie Riefenstahl in Berlin on Aug. 22, 1902, she was the first child of Alfred Riefenstahl, the owner of a heating and ventilation firm, and his wife, Bertha Scherlach.