She will be buried at the Ronald Reagan Presidential Library in Simi Valley, California, next to her husband
Former US First Lady Nancy Reagan has died at her home in Los Angeles, aged 94.
The cause of death was congestive heart failure, according to a statement.
She will be buried at the Ronald Reagan Presidential Library in Simi Valley, California, next to her husband, former US President Ronald Reagan. He died in June 2004.
The former B-movie actress married Reagan in 1952 when he was president of the Screen Actors Guild.
She was California's first lady from 1967-75 while her husband was governor of the state and US First Lady from 1981-89. They had two children together.
During her time in the White House, she led the "Just Say No" anti-drugs campaign.
She was fiercely protective of her husband, and became even more so following the assassination attempt against him outside a Hilton hotel in Washington DC in 1981.
Her consultations with an astrologer, who recommended which days were best for him to leave the White House, influenced the US president's schedule.
Her star-gazing led to clashes with her husband's chief of staff, Donald Regan, and a power struggle that ended with the latter's resignation.
President Barack Obama sent his condolences to Mrs Reagan's family, adding it was "prayerful that she and her beloved husband are together again".
Former President Jimmy Carter also paid tribute to the woman whose husband ousted him from the White House.
He said: "President Reagan has been reunited with his wife and partner but America and the Reagan family have lost a woman of grace and strength."
Leading political figures in the United States have been paying tribute to the late former First Lady on social media.
Nancy Reagan embodied what it means to represent America as First Lady and her dignified and warm demeanor inspired America— Reince Priebus (@Reince) March 6, 2016
Nancy Reagan was an exemplary First Lady and woman. She will be missed. My thoughts and prayers are with her loved ones. RIP Mrs. Reagan— Dr. Rand Paul (@RandPaul) March 6, 2016
My statement on the passing of Nancy Reagan. pic.twitter.com/5ZHXpKGzZB— Lindsey Graham (@LindseyGrahamSC) March 6, 2016
Nancy Reagan always gracious and strong - without her America would never have known President Reagan. Rest in peace, united once again.— George E. Pataki (@GovernorPataki) March 6, 2016
President Bill Clinton and Secretary Hillary Clinton on passing of Nancy Reagan: "Nancy was an extraordinary woman" pic.twitter.com/8hm1N2WDfY— ABC News (@ABC) March 6, 2016
Today our nation mourns the loss of Nancy Reagan, a true example of integrity and grace. My prayers are with the entire Reagan family.— Marco Rubio (@marcorubio) March 6, 2016
My statement on the passing of Former First Lady Nancy Reagan: pic.twitter.com/Kv3zXy0IjF— Governor Christie (@GovChristie) March 6, 2016