Throughout a lifetime of athletic success, hard work, high visibility, and professional and personal challenges both on and off the tennis court, Billie Jean King, an icon of professional tennis, business, and activism, remained deeply committed to gender equality, social parity, and justice. King had fought many battles, overcome many challenges, and knocked down barriers in the sports world and beyond. She had promoted and energized women’s tennis—indeed, tennis as a professional sport—by, among other accomplishments, helping establish the first women’s professional tennis tour, founding the Women’s Tennis Association (WTA) and the Women’s Sports Foundation, and cofounding World TeamTennis (WTT). She was responsible for many changes in tennis, including bringing professionalism to the sport and helping achieve pay parity. This case study details King’s life, including her childhood and her professional tennis career, in which she ranked number one for many years, won 39 major championships, and was regarded by many as one of the greatest tennis players of all time. Starting in the 1960s, with her many tennis championships—including the 1973 “Battle of the Sexes,” in which she defeated Bobby Riggs—King was a household name. But even as her tennis career slowed down, King was still known and recognized internationally for her activism on behalf of women, the LGBTQ community, and social justice and parity. In 2014, she established the Billie Jean King Leadership Initiative, a nonprofit dedicated to diversity, equity, and inclusion. It addressed the critical issues required to achieve inclusive leadership and supported organizations and programs that provided equal opportunity and access, regardless of race, gender, religion, ability, or sexual orientation. This case study examines the many challenges King faced over the years and her efforts to overcome barriers, level the playing field, and promote justice, not just for herself, but for others in and outside the sports world.