Roy E. Disney, the nephew of Walt Disney and a powerful force behind the scenes of Walt Disney Co. who campaigned for the ouster of two chief executives, died Wednesday morning. He was 79.

Disney passed away at Hoag Memorial Hospital Presbyterian in Newport Beach following a yearlong battle with stomach cancer.

The son of longtime Chief Executive Roy O. Disney, Disney’s tumultuous tenure with the company included stints as both filmmaker and company executive. It was marked by his passion for the company’s creative direction and his successful revitalization of its animation division. Disney served as director emeritus until his death.

“He was much more than a valued 56-year company veteran – Roy’s true passion and focus were preserving and building upon the amazing legacy of Disney animation that was started by his father and uncle,” said Walt Disney Co. Chief Executive Bob Iger in a statement. “Roy’s commitment to the art of animation was unparalleled and will always remain his personal legacy and one of his greatest contributions to Disney’s past, present and future.”

Disney began his career with the entertainment behemoth as a filmmaker, writing and directing nature films such as “Perri” and “Mysteries of the Deep.”

Following his father’s death in 1971, the younger Disney, then a member of the company’s board, tried to take a more active role in the company but clashed with other board members. He resigned as an executive in 1977 but remained on the board.

In 1978, Disney, with the help of lawyer Stanley Gold, formed a family-controlled activist investment company known as Shamrock Holdings, which would eventually vault Disney into the ranks of billionaires.

Amid continuing disagreements over the direction and creative focus of Walt Disney Co., Disney resigned from the board in 1984.

The move, part of a larger effort to bring changes to upper management, stirred investors and set in motion a series of events that would lead to the replacement of then-chief executive Ron Miller with a team that included Michael Eisner and Frank Wells.

Disney returned to the board and helped lead a revitalization of the company’s animation department, which he complained had been left to rot as the company shifted focus away from creative pursuits. The company invested in new animation equipment and went on to release a number of highly successful films, including “Beauty and the Beast” and “The Lion King.”

“He was a great man who believed deeply in the art of animation,” said John Lasseter, chief creative officer for Walt Disney and Pixar Animation Studios, in a statement. “He put his heart and soul into preserving Disney’s legendary past, while helping to move the art of animation into the modern age by embracing new technology.”

During the 1990s, the relationship of Disney and chief executive Eisner grew strained. The board declined to renew Disney’s seat on the board, and he announced his resignation in 2003.

Following the announcement, Disney launched a campaign against the company, setting up a Web site, SaveDisney.com, in an attempt to oust Eisner. The battle led to intense criticism of Eisner, who resigned in 2005 and was replaced by Iger. Disney and Gold filed a lawsuit challenging Iger’s selection, but they later mended fences and Disney was appointed director emeritus.

Throughout his life, Disney was more than a corporate titan; he was also a major creative contributor to the company. He worked as a film editor, writer, producer and even cameraman on a number of Disney movies.

Last year, Disney released “Morning Light,” a documentary he co-produced with wife Leslie DeMeuse-Disney chronicling the training of several young sailors for the 2007 Transpacific Yacht Race, a grueling sailing competition spanning 2,225 miles between Los Angeles and Honolulu.

The film project was borne out of Disney’s longtime passion for sailing. He competed in the race, known as Transpac, 16 times in his life, winning it in 1999 with a record pace of seven days, 11 hours, 41 minutes and 27 seconds on his beloved 73-foot yacht, Pyewacket.

Born Jan. 10, 1930, in Los Angeles, Disney grew up immersed in the studio way of life. In 1955, he married Patricia Daily, with whom he would have four children. The couple divorced in 2007.

Disney, a noted philanthropist whose estimated net worth was once in excess of $1 billion, was a mainstay on the Business Journal’s annual list of the wealthiest Angelenos. Following his divorce, however, his net worth fell sharply, and he fell off the list in 2009.

Disney is survived by his wife, Leslie, four children from his earlier marriage and 16 grandchildren.

Funeral services will be private, the company said. Disney’s body will be cremated and his ashes will be scattered at sea.