Redford was born on August 18, 1936, in Santa Monica, California to Martha W. (née Hart) and Charles Robert Redford Sr., a milkman-turned-accountant. He has a stepbrother, william, from his father's remarriage. Redford is of English, Scottish, Irish and Scots-Irish ancestry (his surname originates from Midlothian, Scotland). His paternal great-great grandfather, English Presbyterian Elisha Redford, married Irish-Catholic Mary Ann McCreery in Manchester Cathedral; they emigrated to New York in 1849, immediately settling in Stonington, Connecticut. They had a son named Charles, the first in line to have been given the name.

Redford attended the University of Colorado in the 1950s and received an honorary degree in 1988.

After graduating from high school in 1954, he attended the University of Colorado in Boulder for a year and a half, where he was a member of the Kappa Sigma fraternity. While there, he worked at the restaurant/bar The Sink; a painting of his likeness is prominent in the bar's murals. While at Colorado, Redford began drinking heavily, and as a result lost his half-scholarship and was kicked out of school. Later he traveled in Europe, living in France, Spain, and Italy. He later studied painting at the Pratt Institute in Brooklyn and took classes at the American Academy of Dramatic Arts in New York City.

On September 12, 1958, in Las Vegas, Nevada, Redford married Lola Van Wagenen, who dropped out of college to marry him. They had four children: Scott Anthony (September 1, 1959 – November 17, 1959), Shauna Jean (born November 15, 1960), David James "Jamie" (born May 5, 1962), and Amy Hart Redford (born October 22, 1970). Lola and Redford divorced in 1985.

Redford made his screen debut in Tall Story (1960). It was a minor role. The stars of the film were Anthony Perkins, Jane Fonda (her debut), and Ray Walston. The film was about a college basketball star, played by Perkins, who gets himself into trouble debating as to whether or not he should accept a bribe to throw a basketball game against a team from Russia. After his Broadway success, he was cast in larger feature roles in movies. In 1962 Robert Redford got his second film role in War Hunt. He was cast alongside screen legend Alec Guinness in the war comedy Situation Hopeless ... But Not Serious, in which he played a soldier who has to spend years of his life hiding behind enemy lines. In Inside Daisy Clover (1965), which won him a Golden Globe for best new star, he played a bisexual movie star who marries starlet Natalie Wood, and rejoined her along with Charles Bronson for Pollack's This Property Is Condemned (1966)—again as her lover, though this time in a film which achieved even greater success. The same year saw his first teaming (on equal footing) with Jane Fonda, in Arthur Penn's The Chase. This film marked the only time Redford would star with Marlon Brando. Fonda and Redford were paired again in the popular big-screen version of Barefoot in the Park (1967) and were again co-stars much later in Pollack's The Electric Horseman (1979).

Redford made his film debut in War Hunt (1962). His role in Inside Daisy Clover (1965) won him a Golden Globe for best new star. He starred in Butch Cassidy and the Sundance Kid (1969), which was a huge success and made him a major star. In 1972, he had a critical and box office hit with Jeremiah Johnson (1972), and in 1973 had the greatest hit of his career, the blockbuster crime caper The Sting, for which he was nominated for an Academy Award. The popular and acclaimed All the President's Men (1976) was a landmark film for Redford.

With the financial proceeds of his acting success, starting with his salaries from Butch Cassidy and the Sundance Kid and Downhill Racer, Redford bought an entire ski area on the east side of Mount Timpanogos northeast of Provo, Utah, called "Timp Haven", which was renamed "Sundance". Redford's wife Lola was from Utah and they had built a home in the area in 1963. Portions of the movie Jeremiah Johnson (1972), a film which is both one of Redford's favorites and one that has heavily influenced him, were shot near the ski area.

Redford had long harbored ambitions to work on both sides of the camera. As early as 1969, Redford had served as the executive Producer for Downhill Racer. His first film as Director was 1980's Best Picture winner Ordinary People, a drama about the slow disintegration of an upper-middle class family, for which he won the Academy Award for Best Director. Redford was credited with obtaining a powerful dramatic performance from Mary Tyler Moore, as well as superb work from Donald Sutherland and Timothy Hutton, who also won the Oscar for Best Supporting Actor.

Between 1974 and 1976, exhibitors voted Redford Hollywood's top box-office name. His hits included The Great Gatsby (1974), The Great Waldo Pepper (1975), and Three Days of the Condor (1975). The popular and acclaimed All the President's Men (1976), directed by Alan J. Pakula and scripted once again by Goldman, was a landmark film for Redford. Not only was he the executive Producer and co-star, but the film's serious subject matter—the Watergate scandal—and its attempt to create a realistic portrayal of journalism, also reflected the actor's offscreen concerns for political causes.

He also appeared in a segment of the war film A Bridge Too Far (1977) before starring in the prison drama Brubaker (1980), playing a prison warden attempting to reform the system, and the baseball drama The Natural (1984). Redford continued his involvement in mainstream Hollywood movies, though with a newfound focus on directing. The first film he directed, Ordinary People, which followed the disintegration of an upper-class American family after the death of a son, was one of the most critically and publicly acclaimed films of the decade, winning four Oscars, including Best Director for Redford himself, and Best Picture. His follow-up directorial project, The Milagro Beanfield War (1987), failed to generate the same level of attention. Sydney Pollack's Out of Africa (1985), with Redford in the male lead role opposite Meryl Streep, became an enormous critical and box office success and won seven Oscars including Best Picture, proving to be Redford's biggest success of the decade and Redford and Pollack's most successful of their six movies together. His next film, Legal Eagles (1986), was only a minor success at the box office.

The first film that Redford directed, Ordinary People (1980), was one of the most critically and publicly acclaimed films of the decade, winning four Oscars including Best Picture and the Academy Award for Best Director for Redford. In 1980, he starred in Brubaker (1980). He starred in Out of Africa (1985), which was an enormous critical and box office success, and won seven Oscars including Best Picture. He released his third film as a Director, A River Runs Through It, in 1992.

Redford did not direct again until The Milagro Beanfield War (1988), a well-crafted, though not commercially successful, screen version of John Nichols' acclaimed novel of the Southwest. The Milagro Beanfield War is the story of the people of Milagro, New Mexico (based on the real town of Truchas in northern New Mexico), overcoming big developers who set about to ruin their community and force them out because of tax increases. Other directorial projects have included the period drama A River Runs Through It (1992), based on Norman Maclean's novella, and the exposé Quiz Show (1994), about the quiz show scandal of the late 1950s. In the latter film, Redford worked from a screenplay by Paul Attanasio with noted Cinematographer Michael Ballhaus and a strong cast that featured Paul Scofield, John Turturro, Rob Morrow, and Ralph Fiennes. Redford handpicked Morrow for his part in the film (Morrow's only high-profile feature film role to date), because he liked his work on Northern Exposure. Redford also directed Matt Damon and Will Smith in The Legend of Bagger Vance (2000). In 2010, Redford released The Conspirator, a period drama revolving around the assassination of Abraham Lincoln. Despite a subject matter of personal interest to Redford, the film received mixed reviews and proved to be a flop at the box office.

In 1989, the National Audubon Society awarded Redford its highest honor, the Audubon Medal.

Redford supports environmentalism, Native American rights, LGBT rights, and the arts. He has also supported advocacy groups, such as the Political Action Committee of the Directors Guild of America. Redford has on occasion also supported Republicans, including Brent Cornell Morris in his unsuccessful campaign for the Republican nomination for Utah's 3rd congressional district in 1990. Redford also supported Gary Herbert, another Republican and a friend, in Herbert's successful 2004 campaign to be elected Utah's Lieutenant Governor. Herbert later became Governor of Utah. Redford is an avid Environmentalist and is a trustee of the Natural Resources Defense Council. He endorsed Democratic President Barack Obama for re-election in 2012. Redford is the first quote on the back cover of Donald Trump's book Crippled America saying of Trump “I'm glad he's in there, being the way he is." But Redford's comment was intended to be sarcastic, as the rest of the comment follows, "He's got such a big foot in his mouth I'm not sure you could get it out.”

In 1995, he received an honorary Doctor of Humane Letters degree from Bard College. He was a 2002 Lifetime Achievement Award/Honorary Oscar recipient at the 74th Academy Awards.

Since founding the nonprofit Sundance Institute in Park City, Utah, in 1981, Redford has been deeply involved with independent film. Through its various workshop programs and popular film festival, Sundance has provided much-needed support for independent filmmakers. In 1995, Redford signed a deal with Showtime to start a 24-hour cable television channel devoted to airing independent films. The Sundance Channel premiered on February 29, 1996.

He appeared as a disgraced Army general sent to prison in the prison drama The Last Castle (2001), directed by Rod Lurie. In the same year, Redford reteamed with Brad Pitt for Spy Game, another success for the pair but with Redford switching this time from Director to actor. Redford, a leading environmental Activist, narrated the IMAX documentary Sacred Planet (2004), a sweeping journey across the globe to some of its most exotic and endangered places. In The Clearing (2004), a thriller co-starring Helen Mirren, Redford was a successful businessman whose kidnapping unearths the secrets and inadequacies that led to his achieving the American Dream.

Redford stepped back into producing with The Motorcycle Diaries (2004), a coming-of-age road film about a young medical student, Ernesto "Che" Guevara, and his friend Alberto Granado. It also explored political and social issues of South America that influenced Guevara and shaped his Future. With five years spent on the film's making, Redford was credited by Director Walter Salles for being instrumental in getting it made and released.

In December 2005, he received the Kennedy Center Honors for his contributions to American culture. The honors recipients are recognized for their lifetime contributions to American culture through the performing arts: whether in dance, music, theater, opera, motion pictures or television.

The Sundance Film Festival caters to independent filmmakers in the United States and has received recognition from the industry as a place to open films. In 2008, Sundance exhibited 125 feature-length films from 34 countries, with more than 50,000 attendees. The name Sundance comes from his Sundance Kid character. Redford also owned a restaurant called Zoom, located on Main Street in the former mining town of Park City, until its closure in May 2017.

In July 2009, Redford married his longtime partner, Sibylle Szaggars, at the Louis C. Jacob Hotel in Hamburg, Germany. She had moved in with Redford in the 1990s and shared his home in Sundance, Utah.

On October 14, 2010, he was appointed chevalier of the Légion d'honneur. He was a 2010 recipient of the New Mexico Governor's Award for Excellence in the Arts

In May 2011, Alfred A. Knopf published Robert Redford: The Biography by Michael Feeney Callan, written over fifteen years with Redford's input and drawn from his personal papers and diaries.

Redford is opposed to the TransCanada Corporation's Keystone Pipeline. In 2013, he was identified by its CEO, Russ Girling, for leading the anti-pipeline protest movement.

In April 2014, Redford, a Pitzer College Trustee, and Pitzer College President Laura Skandera Trombley announced that the college will divest fossil fuel stocks from its endowment; at the time, it was the higher education institution with the largest endowment in the US to make this commitment. The press conference was held at the LA Press Club. In November 2012, Pitzer launched the Robert Redford Conservancy for Southern California Sustainability at Pitzer College. The Redford Conservancy educates the next generation of students to create solutions for the most challenging and urgent sustainability problems.

On May 24, 2015, Redford delivered the commencement address and received an honorary degree from Colby College in Waterville, Maine. On November 22, 2016, President Barack Obama honored Redford with a Presidential Medal of Freedom. In 2017, Golden Lion for Lifetime Achievement at the 74th Venice Film Festival

On November 10, 2016, Redford told Dylan Redford, his grandson, that he’ll retire from acting after his next two movies are finished. But Redford's publicist told Deadline that he's not retiring from acting anytime soon, explaining that: "he has several projects coming down the pike." One of those projects is Pete's Dragon, a remake of the 1977 Disney film. Redford plays Mr. Meacham, an old wood carver who once met a dragon.

Most recently, Sundance Productions produced Chicagoland (CNN), Cathedrals of Culture (Berlin Film Festival), The March (PBS) and Emmy Nominee All The President’s Men Revisited (Discovery), Isabella Rossellini’s Green Porno Live!, and To Russia With Love on Epix.