Karola Ruth Westheimer (née Siegel; born June 4, 1928), better known as Dr. Ruth, is a German-American sex–therapist, talk show host, author, professor, and Holocaust survivor.

Westheimer was born in Germany to a Jewish family. As the Nazis came to power, her parents sent the ten-year-old girl to a school in Switzerland for safety, remaining behind themselves because of her elderly grandmother. They were both subsequently sent to concentration camps by the Gestapo, where they were killed. After World War II ended, she immigrated to British-controlled Mandatory Palestine. Despite being only 4 feet 7 inches (1.39 m) tall and 17 years of age, she joined the Haganah, and was trained as a sniper, but never saw combat. On her 20th birthday, Westheimer was seriously wounded in action by an exploding shell during a mortar fire attack on Jerusalem during the 1947–1949 Palestine war, and almost lost both of her feet. Moving to Paris, France two years later, she studied psychology at the Sorbonne. Immigrating to the United States in 1956, she worked as a maid to put herself through graduate school, earned an M.A. degree in sociology from The New School in 1959, and earned a doctorate at 42 years of age from Teachers College, Columbia University, in 1970. Over the next decade, she taught at a number of universities, and had a private sex therapy practice.

Westheimer's media career began in 1980 with the radio call-in show Sexually Speaking, which continued until 1990. In 1983 it was the top-rated radio show in the area, in the country's largest radio market. She then launched a television show, The Dr. Ruth Show, which by 1985 attracted 2 million viewers a week. She became known for giving serious advice while being candid, but also warm, cheerful, funny, and respectful, and for her tag phrase; "Get some". The New York Times noted in 1984 that she had risen "from obscurity to almost instant stardom." She hosted several series on the Lifetime Channel and other cable television networks from 1984 to 1993. She became a household name and major cultural figure, appeared on several network TV shows, co-starred in a movie with Gérard Depardieu, appeared on the cover of People, sang on a Tom Chapin album, appeared in several commercials, and hosted Playboy videos. She is the author of 45 books on sex and sexuality.

The one-woman 2013 play Becoming Dr. Ruth, written by Mark St. Germain, is about her life, as is the 2019 documentary, Ask Dr. Ruth, directed by Ryan White. Westheimer has been inducted into the Radio Hall of Fame, and awarded the Magnus Hirschfeld Medal, the Ellis Island Medal of Honor, the Leo Baeck Medal, the Planned Parenthood Margaret Sanger Award, and the Order of Merit of the Federal Republic of Germany.