Her son, Todd Fisher, said Reynolds died Wednesday.
"She's now with Carrie and we're all heartbroken," Fisher said from Cedars-Sinai Medical Center, where his mother was taken by ambulance earlier Wednesday.
He said the stress of his sister's death on Tuesday "was too much" for Reynolds. Carrie Fisher, who was 60, had been hospitalized since Friday.
"She said, 'I want to be with Carrie,'" her son said. "And then she was gone."
Reynolds enjoyed the heights of show business success and endured the depths of personal tragedy. She lost one husband to Elizabeth Taylor and two other husbands plundered her for millions. Fisher, who found lasting fame as Princess Leia in "Star Wars" and struggled for much of her life with drug addiction and mental health problems, died after falling ill on a plane.
Reaction to Reynolds' death was swift.
"Debbie Reynolds, a legend and my movie mom. I can't believe this happened one day after Carrie," Albert Brooks, who played opposite Reynolds in "Mother," said on Twitter.
"I can't imagine what Carrie Fisher and Debbie Reynolds' family are going through this week. I send all of my love," Ellen DeGeneres tweeted.
Reynolds found superstardom early. After two minor roles at Warner Bros. and three supporting roles at MGM, studio boss Louis B. Mayer cast her in "Singin' in the Rain," despite Kelly's objections. She was 19 with little dance experience, and she would be appearing with two of the screen's greatest dancers, Donald O'Connor and Kelly.
"Gene Kelly was hard on me, but I think he had to be," Reynolds, who more than held her own in the movie, said in a 1999 Associated Press interview. "I had to learn everything in three to six months. Donald O'Connor had been dancing since he was three months old, Gene Kelly since he was 2 years old."
The 1964 Meredith Willson musical "The Unsinkable Molly Brown," with Molly's defiant song "I Ain't Down Yet," brought Reynolds her only Academy Award nomination. She also received a Tony nomination in 1973 for her starring role in the Broadway revival of "Irene," in which her daughter also appeared.
After her transition from starlet to star, Reynolds became popular with teenage girls and even more so when in 1955 she married Eddie Fisher, the pop singer whose fans were equally devoted.
The couple made a movie together, "Bundle of Joy," which seemed to mirror the 1956 birth of Carrie. The Fishers also had a son, Todd, named for Eddie's close friend and Taylor's husband, showman Mike Todd.
During this period, Reynolds had a No. 1 hit on the pop charts in 1957 with "Tammy," the Oscar-nominated song from her film "Tammy and the Bachelor." But the Cinderella story ended after Mike Todd died in a 1958 airplane crash. Fisher consoled the widow and soon announced he was leaving his wife and two children to marry Taylor.
The celebrity world seemed to lose its mind. Taylor was assailed as a husband stealer, Fisher as a deserter. Reynolds won sympathy as the innocent victim, a role emphasized when she appeared before news cameras with diaper pins on her blouse. A cover headline in Photoplay magazine in late 1958 blared: "Smiling through her tears, Debbie says: I'm still very much in love with Eddie."
Fisher's singing career never recovered, but Reynolds' film career flourished. She starred with Glenn Ford in "The Gazebo," Tony Curtis in "The Rat Race," Fred Astaire in "The Pleasure of His Company," Andy Griffith in "The Second Time Around," with the all-star cast in "How the West Was Won" and Ricardo Montalban in "The Singing Nun."
She also provided the voice of Charlotte in the 1973 animated "Charlotte's Web."
But over the years, her marital woes continued.
In 1960 Reynolds married shoe magnate Harry Karl. The marriage ended in 1973 when she discovered that Karl, a compulsive gambler, had devastated her assets.
Reynolds' third marriage, to Virginia businessman Richard Hamlett in 1984, proved equally disastrous. In 1992, against friends' advice, she paid $10 million to buy and convert a faded Las Vegas hotel into the Debbie Reynolds Hotel and Casino. She performed nightly and conducted tours of her movie memorabilia.
Reynolds, who ended up filing for bankruptcy in 1997 and selling the property at auction the next year, accused Hamlett of making off with her money.
"All of my husbands have robbed me blind," she asserted in 1999. "The only one who didn't take money was Eddie Fisher. He just didn't pay for the children."
In her later years, Reynolds continued performing her show, traveling 40 weeks a year. She also appeared regularly on television, appearing as John Goodman's mother on "Roseanne" and a mom on "Will & Grace." Her books included the memoirs "Unsinkable" and "Make 'Em Laugh."
In 1996 she won critical acclaim in the title role of Albert Brooks' movie "Mother." Reynolds and her daughter were featured together in the HBO documentary "Bright Lights," scheduled for release in 2017.
Mary Frances Reynolds spent the first eight years of her life in Depression-era poverty in El Paso, Texas, where she was born on April 1, 1932. Her father, a carpenter for the Southern Pacific Railroad, was transferred to California and the family settled in Burbank, near Warner Bros. studio.
The girl flourished, winning 48 Girl Scout merit badges, excelling in sports and playing French horn and bass viola in the Burbank Youth Symphony. Girlfriends persuaded her to enter the beauty contest for Miss Burbank, and she won over the judges.
Eventually, she teamed up with Taylor — long since divorced from Fisher — and two other veterans, Joan Collins and MacLaine, for the 2001 TV movie "These Old Broads." The script, co-written by Reynolds' daughter, was about aging, feuding actresses who get together for a reunion show. Reynolds would look back wryly on the Taylor affair, acknowledging that no man could have resisted her and that she actually voted for Taylor when she was up for best actress in 1960. The former romantic rivals had reconciled years before Taylor died in 2011; Reynolds recalled they had both been passengers on the Queen Elizabeth.
"I sent a note to her and she sent a note to me in passing, and then we had dinner together," she told The Huffington Post a few months after Taylor's death. "She was married to Richard Burton by then. I had been remarried at that point. And we just said, 'Let's call it a day.' And we got smashed. And we had a great evening, and stayed friends since then."
Reynolds received an honorary Oscar in 2015, the Jean Hersholt Humanitarian Award, but was too ill to attend the ceremony. Her granddaughter, actress Billie Lourd, accepted the statuette in her honor.
"I'm so sorry that I'm sick, but I am thrilled beyond words, shocked, and you couldn't be more amazed that a little girl from Burbank even came near this sort of accolade," she said in a pre-recorded statement.
She was recognized for her decades-long commitment to various charities, including the mental-health organization she founded, the Thalians.
AP entertainment reporters Hillel Italie in New York and Sandy Cohen and Anthony McCartney in Los Angeles contributed to this report. The late Associated Press writer Bob Thomas contributed biographical material to this report.
Copyright 2016 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.