Nancy Sinatra Sr., the childhood sweetheart of Frank Sinatra who became the first of his four wives and the mother of his three children, has died. She was 101.

Her daughter, Nancy Sinatra Jr., tweeted that her mother died Friday and a posting on her web page said she died at 6.02pm but didn't indicate where she died.

"She was a blessing and the light of my life," her daughter said.

Frank and Nancy Sinatra smile broadly as they leave a Hollywood nightclub in 1946. Credit:AP

Attempts to reach representatives for Sinatra Jr. late Friday were unsuccessful.