Kirk Douglas, known as one of the most beloved tough guys in Hollywood history on screen and a defender of blacklisted artists off screen, died Wednesday at age 103.

Michael Douglas, the actor's Oscar-winning son, announced his death in an Instagram post on behalf of the family.

"To the world, he was a legend, an actor from the golden age of movies who lived well into his golden years, a humanitarian whose commitment to justice and the causes he believed in set a standard for all of us to aspire to," he wrote.

Douglas, who bravely and publicly fought his way back from a severe stroke in 1996, will be remembered for the grit and determination he showed on screen in action epics like "Spartacus" and "20,000 Leagues Under the Sea," biopics like "Lust for Life" and more intimate character studies like "Lonely Are the Brave." But his commitment to higher ideals in the film industry proved even more dramatic.

Douglas was responsible for helping to break Hollywood's infamous blacklist at the height of Cold War paranoia when he was instrumental in hiring and crediting the legendary screenwriter Dalton Trumbo, a member of the so-called Hollywood Ten, for his work on "Spartacus."

He was also a committed philanthropist.

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"I've known Kirk Douglas personally and appreciate his friendship," President Jimmy Carter said as he awarded Douglas the Presidential Medal of Freedom, the nation's highest civilian honor, in 1981. "But more than that, I have known how dedicated he is to using his talent as an actor and a director and the esteem with which he's held by his own people in spreading the good news about this country and explaining our purposes, our ideals, our commitments and our achievements, our hopes and our dreams to people around the world."

Douglas' progressive values may been the product of his upbringing as the poor child of Jewish immigrants from what's now Belarus — his birth name was Issur Danielovitch — who grew up in Amsterdam, New York.

After cutting his teeth as a stage actor and scoring strong supporting roles in classic films like "Out of the Past," Douglas would eventually emerge as a star in his own right in the 1949 boxing drama "Champion," for which he earned the first of three Academy Award nominations for best actor. (He would take home a Lifetime Achievement Oscar in 1996.)

In that film, and in his subsequent hits that followed, Douglas broke with the tradition of unflappable leading men by portraying complex and often morally conflicted characters whp tested audiences' sympathies.

Meanwhile, in tough, trenchant films like "Ace In the Hole," "Paths of Glory" and "Seven Days in May," Douglas didn't shy away from challenging subject matter like corruption of the press and the military.

Douglas pursued his passions without sacrificing his popular appeal: The movie trade publisher Quigley Publishing ranked him among the top 25 box office stars for six straight years beginning in 1957. And even as his production tailed off in later decades, the cleft-chinned star remained a virile sex symbol well into his 60s.

The pace Douglas kept as a perpetual A-lister took a toll on his relationship with his family. He split from Michael's mother when his famous son was only 6 years old.

"He was a rager early on. He was overworked. He was doing five-plus pictures a year," Michael Douglas told Men's Journal in 2013. "I just sort of stayed out of his way, but he did the best he could."

Over the years, the two stars repaired their relationship and would even appear alongside each other (along with Kirk's embattled grandson Cameron) in the 2003 drama "It Runs In the Family." And he stood by Michael's side when he battled stage 4 cancer in 2010.

Julie Newmar, Leslie Parrish and Mitzi Gaynor on a studio set with Kirk Douglas in Hollywood in 1962. Don Brinn / AP

He also began blogging in his 90s, attracting a new generation of fans, and his 12th book, "Kirk and Anne: Letters of Love, Laughter, and a Lifetime in Hollywood," co-written with his wife of 62 years, Anne Buydens Douglas, was published in 2017.

Douglas received a standing ovation at the 2018 Golden Globe awards, sharing the spotlight with his daughter-in-law Catherine Zeta-Jones, who presented an award.

Douglas is survived by his wife and three sons, Michael, Peter and Joel Douglas. His youngest son with Buydens, Eric, died in 2004 of what was ruled an accidental drug overdose.