Sister Marion Irvine  is an American nun and former marathon runner. Sister Irvine participated in the United States Olympic Trials in track and field in 1984 when she was 54 years old. She became the oldest person to participate in Olympic trials. Following the Trials, she regularly ran on the marathon circuit and gained attention from the media, along with the nickname "The Flying Nun". Irvine broke numerous age-group records in distance running events during her career, and has been inducted into multiple running halls of fame.

Sister Marion Irvine spent the years after the end of her running career campaigning for social issues, and credited her attendance at the 1999 World Trade Organization protests as the driving factor behind her involvement. She has been a critic of the death penalty, globalization, and the Iraq War.