She became first lady in January 1981 when Ronald Wilson Reagan became 40th president and served in that role for eight years, during which time she became known for the "Just say no" slogan in her anti-drug campaign.
The former Nancy Davis married fellow actor Ronald Reagan in 1952 and was regarded as his fiercely loyal anchor as he ascended to the governorship of California and presidency.
Ronald Reagan died in June, 2004 after battling Alzheimer's disease.
Nancy Reagan is survived by daughter Patti, son Ron and stepson Michael.
"I am saddened by the passing of my stepmother Nancy Reagan," Michael Reagan said in a Tweet posted Sunday morning. "She is once again with the man she loved. God Bless."
Nancy Reagan will be buried at the Ronald Reagan Presidential Library in Simi Valley, California, next to her husband, according to her representative.
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