Her eldest daughter, Nancy Sinatra Jr., confirmed the news on Twitter — writing, “My mother passed away peacefully tonight at the age of 101. She was a blessing and the light of my life. 😢💙.”
On her website, Nancy Jr. revealed that her mother died at 6:02 p.m.
“This may be the saddest post I’ve ever had to write,” Nancy Jr. said. “She fought hard to remain on this earth but time got the better of her.”
“Godspeed, Momma and thank you for everything you did for us and for the world,” she added.
Reps for Nancy Jr. did not immediately respond to PEOPLE’s request for comment.
Nancy Sr.’s death comes two decades after the death of “Ol’ Blue Eyes,” who died in 1998 at the age of 82 of a heart attack.
Born Nancy Barbato, she met Frank when they were both teenagers. The pair married in 1939 in Jersey City, New Jersey — Nancy Sr.’s hometown.
They’d live there as newlyweds for years, with Frank working as a singing waiter to get his music career started and Nancy Sr. working as a secretary while raising daughter Nancy Jr., born in 1940, and son Frank Jr., born in 1944.
Eventually, the family would move to Los Angeles, where Frank would find fame on the charts and on the movie screen. Daughter Christina Sinatra, known as Tina, was born in 1948.
But a headline-making extramarital affair drove the couple apart. They divorced in 1951, with Frank famously marrying actress Ava Gardner just weeks after the papers were signed. After that, he’d have marriages to Mia Farrow and Barbara Marx.
At the time of their divorce, Nancy Sr. was 33. She was given custody of their children, their home, a Cadillac and a percentage of his wealth.
She devoted her life to her children, PEOPLE reported in 1986, but made no secret of her desire to reconcile with their father.
Nancy Sr. never remarried, preferring to retain the status of a divorced woman and be Mrs. Nancy Sinatra for life rather than lose the Sinatra name.
“Once you’ve had the best…” she told friends.
Nancy Sr. is survived by Nancy Jr., 78, and Tina, 70. Frank Jr. died of cardiac arrest in 2016 at the age of 72.