Kathrine Virginia "Kathy" Switzer (born January 5, 1947, in Amberg,Germany) is an American author, television commentator and marathon runner, best known for being the first woman to run the Boston Marathon as a numbered entry, in 1967.

After her coach insisted a marathon was too far to run for a "fragile woman", Switzer trained for and completed the 1967 Boston Marathon under entry number 261 with the Syracuse Harriers athletic club. It was another five years before women were officially allowed to compete . Her finishing time of approximately 4 hours and 20 minutes was nearly an hour behind the first female finisher, Bobbi Gibb (who ran unregistered). She registered under the gender-neutral "K. V. Switzer", which she said was not done to mislead the officials. She claimed she had long used "K. V. Switzer" to sign the articles she wrote for her university paper. Switzer was issued a number through an "oversight" in the entry screening process, and was treated as an interloper when the error was discovered. Race official Jock Semple attempted to physically remove her from the race. Switzer claims he shouted, "Get the hell out of my race and give me those numbers." Switzer's boyfriend Tom Miller, who was running with her, shoved Semple aside and sent him flying, allowing her to proceed. Photographs taken of the incident made world headlines.

Afterwards, Boston Athletic Association director Will Cloney was asked his opinion of Switzer competing in the race. Cloney said, "Women can't run in the Marathon because the rules forbid it. Unless we have rules, society will be in chaos. I don't make the rules, but I try to carry them out. We have no space in the Marathon for any unauthorized person, even a man. If that girl were my daughter, I would spank her."

Because of her run, the AAU barred women from all competitions with male runners, with violators losing the right to compete in any races. Switzer, with other women runners, tried to convince the Boston Athletic Association to allow women to participate in the marathon. Finally, in 1972, women were welcome to run the Boston Marathon officially for the first time ever. Jock Semple, the man who had previously attempted to remove Switzer from the race, was instrumental in this formal admission of female runners.