“If you don't have good running form, there's only so fast you can go.”

American-born Irish middle-distance runner

Mary Cecilia Cain is an American-born Irish middle-distance runner from Bronxville, New York. Born in 1996, she became known for her early rise in track and field and for representing the United States at the 2013 World Championships in Athletics at the age of 17 years and 3 months. She won the 2014 World Junior title in the 3000 meter event and stood out as the youngest female athlete ever to compete for the United States at a World Championships meet. Her public profile is tied to competitive running, especially middle-distance events and the results she achieved at a very young age.