Redford was acclaimed for films including All The President's Men, Butch Cassidy And The Sundance Kid and The Sting, and was also known for his activism, as well as directing films such as Ordinary People, for which he won an Oscar, and A River Runs Through It.
"Very sad news, very sad day," DiCaprio told the PA news agency at the premiere of One Battle After Another in London.
"We lost an absolute legend in our industry. I admire him for not only his work as an actor, but as a director with Quiz Show.
"We have a film tonight that we're premiering, that is a political thriller in a lot of ways, and he was the one that created the foundation for all that, with All The President's Men, Three Days Of The Condor.
"But more so than anything, I've said it over and over again, he was an avid environmental advocate, was a member of the NRDC (Natural Resources Defence Council) like me, and he was a hero to a lot of people in our industry, including myself, so it's a huge loss."
Actor Benicio Del Toro paid tribute to Redford's work as an advocate for independent cinema, which led to his creation of the Sundance Institute, known for its annual Sundance Film Festival."What he did for young film-makers with Sundance in America, in the USA, it's unprecedented, and it was amazing," Del Toro told PA.
The Sundance Film Festival has helped launch the careers of directors including Quentin Tarantino and Steven Soderbergh, and provided a launchpad for films such as Reservoir Dogs, Sex, Lies And Videotape, The Blair Witch Project, Little Miss Sunshine and recent Oscar-winner Coda.
A Beautiful Mind director Ron Howard called the Oscar-winning actor an "artistic gamechanger".
"RIP and thank you Robert Redford, a tremendously influential cultural figure for the creative choices made as an actor/producer/director and for launching the Sundance Film Festival which supercharged America's Independent Film movement. Artistic Gamechanger," he wrote on social media platform X.
Meryl Streep - who starred opposite Redford in 1985's Out Of Africa and Lions For Lambs in 2007 - penned: "One of the lions has passed."
Actor Demi Moore, who starred alongside Redford in 1993's Indecent Proposal, said his legacy will continue.
"The world has lost an incredible actor, director, husband, father, friend ... Robert's legacy will live on forever in so many ways and I will carry the many memories we share close to my heart," she said on social media.
"What I would do for just one more dance."
Barbra Streisand called Redford "one of a kind".
"Bob was charismatic, intelligent, intense, always interesting - and one of the finest actors ever.
"The last time I saw him, when he came to lunch, we discussed art and decided to send each other our first drawings. He was one of a kind and I'm so grateful to have had the opportunity to work with him."
US President Donald Trump described Redford as "great", telling reporters "he had a series of years where there was nobody better".
A statement from Redford's publicist revealed the film great's death.
"Robert Redford passed away on September 16, 2025, at his home at Sundance in the mountains of Utah - the place he loved, surrounded by those he loved," it said.
"He will be missed greatly. The family requests privacy."
13°C