margaret court was the defending champion, and successfully defended her title, defeating rosie casals in the final, 6–2, 2–6, 6–1, to win the women's singles tennis title at the 1970 us open. this was court's fourth us open title, her fifth consecutive grand slam tournament title and her twentieth grand slam tournament win overall. by holding the four major titles at the same time, court became the first woman in the open era to complete a grand slam.