Born to Maggie and Tom Courtney in October 1995, Kate Courtney grew up in Marin County, California at the base of Mount Tamalpais, which is considered to be the birthplace of mountain biking. Courtney was introduced to cycling at a young age by her father and they would ride a mountain-bike tandem up Mount Tamalpais together. Her interest in cycling was piqued when, as a freshman, she joined her school mountain bike team at Branson High School. While at high school, Courtney competed for the USA National Team and Whole Athlete Development Team in events around the World. In 2012, Courtney became the first American woman to win a UCI Mountain Bike World Cup in the Junior category.