Kathleen Winsor (October 16, 1919 – May 26, 2003) was an American author best known for her first work, the 1944 historical novel Forever Amber. Considered racy for its time, the novel quickly became a runaway bestseller, attracting both acclaim and criticism for its depictions of sexuality. Despite writing seven other novels, none matched the success of her debut.

Winsor was raised in Berkeley, California. At the age of 18, Winsor made a list of her life goals, which included the aspiration to write a best-selling novel. She graduated in 1938 from the University of California, Berkeley. During her school years, she married All-American college football player Robert Herwig. In 1937, she began writing a thrice-weekly sports column for the Oakland Tribune. Although that job only lasted a year, she later returned to the newspaper to work as a receptionist, a position from which she was fired in 1938 as the newspaper trimmed its workforce.

Winsor's interest in the Restoration period was sparked through her husband, Robert Herwig. He was writing a paper on Charles II, and out of boredom, Winsor began to read about the period, which eventually inspired her to write Forever Amber.