Mary Teresa Slaney is an American retired middle-distance runner. During her career, she won gold medals in the 1500 meters and 3000 meters at the 1983 World Championships and was the world-record holder in the mile, 5000 meters and 10,000 meters. In total, she set 17 official and unofficial world records, and she was the first woman to break 4:20 for the mile. She also set 36 U.S. national records at distances ranging from 800 meters to 10,000 meters, and has held the U.S. record in the 2000 meters and 3000 meters since the early 1980s, while her 1500 meters record stood for 32 years and her mile record stood for 38 years. In 2003, she was inducted into the National Track and Field Hall of Fame.

The 1500 metres or 1,500-metre run is the foremost middle distance track event in athletics. The distance has been contested at the Summer Olympics since 1896 and the World Championships in Athletics since 1983. It is equivalent to 1.5 kilometers or approximately 15⁄16 miles. The event is closely associated with its slightly longer cousin, the mile race, from which it derives its nickname "the metric mile".