No cause of death was given.
Nancy Sinatra Senior has died aged 101, it's been confirmed.
"She was a blessing and the light of my life".
Frank Sinatra left his Nancy for Ava Gardner in the early 1950s.
Frank and Nancy met in 1934 at the New Jersey holiday resort of Long Branch when he was 19 and she was 17.
Sinatra went on to marry three other women - Gardner, Mia Farrow and Barbara Marx - but had a string of affairs with some of Hollywood's leading ladies, including Judy Garland, Lauren Bacall, Marilyn Monroe and Angie Dickinson.
Though her husband would remarry three more times, Nancy, a staunch catholic, never remarried.
After Sinatra became a pop-music sensation in the 1940s, the couple moved to Los Angeles, where the singer would also become a movie star, raconteur and notorious womanizer.
The Sinatras separated in 1950 and their divorce was finalised in 1951.
After the gossip over the divorce and Gardner marriage died down, Nancy Sinatra devoted herself to family and numerous celebrity friends, largely withdrawing from the spotlight.
She is thought to have remained friends with her ex-husband up until his death and he would reportedly put in requests for various Italian dishes she was a expert in over the years. Sinatra's hit song, "She's Funny That Way", plays in the background.