She was known as his fierce protector and perhaps his closest advisor. When his presidency was jeopardized by the Iran-Contra affair in the mid-1980s, she took a decisive role in imposing new leadership around him.
But she was also known for a decidedly unconventional aspect of White House life: using an astrologer. Here's the story from The Times archives.
Who did Reagan use as her astrologer?
Her name was Joan Quigley.
In Nancy Reagan's memoir, "My Turn," the former first lady said she called Quigley in the aftermath of an assassination attempt on the president. "I'm scared every time he leaves the house," she told Quigley, seeking advice on the timing of President Reagan's comings and goings.
Quigley later said that over the next seven years, she issued guidance, for pay, that went far beyond mundane scheduling to matters of diplomacy, Cold War politics and even the timing of the president's cancer surgery.
Nancy Reagan downplayed Quigley's influence when news that the first family had an astrologer was met with a firestorm of criticism and jokes. But the scorned Aries astrologer struck back.
"I would participate in a more intimate way," she said in a 1990 Times interview, "than the publicly recognized insiders of greatest importance."
What was the reaction when the news became public?
For the most part, Nancy Reagan was mocked.
The New York Post had a headline saying, "Astrologer Runs The White House," and one joke suggested a Cabinet post in charge of voodoo be created.
Reagan, who said she was highly embarrassed by the revelation (payments to Quigley had been made through a third party to try to keep the relationship secret), wrote in her 1989 book, "While astrology was a factor in determining Ronnie's schedule, it was never the only one, and no political decision was ever based on it."
But there was debate over exactly how much influence Quigley actually had. She claimed a bigger role in her 1990 book, "What Does Joan Say?: My Seven Years As White House Astrologer to Nancy and Ronald Reagan."
"I was responsible for timing all press conferences," she said, "most speeches, the State of the Union addresses, the takeoffs and landings of Air Force One. I picked the time of Ronald Reagan's debate with [Jimmy] Carter and the two debates with Walter Mondale; all extended trips abroad as well as the shorter trips and one-day excursions."
Quigley spoke to the president only once, briefly, at a 1985 state dinner. But she said on "CBS This Morning" in 1990 that "through Nancy, I really had a direct line to the president."
The legacy lived on. In 2008, presidential candidate Barack Obama called Reagan to apologize for remarks some thought were insensitive. Obama said: "I didn't want to get into a Nancy Reagan thing about doing any séances."
Whatever happened to Quigley?
Her Reagan link made her something of a celebrity, and she wrote books and appeared on national television shows. As The Times reported in her obituary: "She briefly surfaced in 2000 when she attempted to start a paid astrology online service, but it seems it wasn't in the stars."
She died in 2014.