Sister Madonna Buder, S.F.C.C., or the Iron Nun (born July 24, 1930) is a self-styled religious sister from Spokane, Washington. Sister Madonna is the current world record holder for the oldest person to ever finish an Ironman Triathlon.
Buder was born in St. Louis, Missouri in July 1930, and entered the convent at age 23. In 1970 she left the congregation to which she had belonged to join 38 other Sisters from different and varying backgrounds to establish a new and non-traditional community of Sisters. As a member of the non-canonical Sisters for Christian Community, independent of the authority of the Roman Catholic Church, Sister Madonna has had the freedom to choose her own ministry and lifestyle.
Buder began training at age 48 at the behest of Father John who told her it was a way of tweaking, "mind, body, and spirit" and for the relaxation and calmness it can bring an individual. She completed her first triathlon at age 52 and first Ironman event at age 55 and has continued ever since.
Buder is well known in the Triathlon community for her achievements in age group races. She has completed over 325 triathlons including 45 Ironman Distances. At the 2005 Hawaii Ironman, at age 75, The Iron Nun became the oldest woman ever to complete the race, finishing 1 hour before the 17-hour midnight cut-off time. At the 2006 Hawaii Ironman, at age 76, she again became the oldest woman ever to complete the race, finishing with a time of 16:59:03.
During her sporting career, Buder has worked hard at also raising money for various charities. She is quoted as saying, "I train religiously."
On August 24, 2008, Sister Madonna participated in the Ironman race held in Penticton, British Columbia, Canada. She was unable to finish the race by a factor of seconds as she was unable to reach the finish line within the 17 hours cut-off limit. However, 371 days later, on August 30, 2009, Sister Madonna completed Ironman Canada (Penticton, British Columbia) in a time of 16:54:30. This accomplishment broke her own record of being the oldest female to complete the Ironman distance at 79 years old. In fact the Ironman organization has had to add new age brackets as the Sister gets older. Unfortunately, although Sister Madonna started the 2010 Ironman Canada competition at the age of 80 she was unable to complete the course, due to a wetsuit issue. She competed in the 2011 Ironman Canada competition but missed the bike cut-off by 2 minutes.
She was willing to compete in an Ironman triathlon again in 2012 as she wanted to open up an 80+ age category and be the oldest person, male or female, to finish an Ironman triathlon. Buder thus became the overall Ironman world record holder in age at age 82 by finishing the Subaru Ironman Canada on August 26, 2012. She beat the record previously held by 81-year-old Lew Hollander who finished the Ironman Kona World Championship in 2011. Sister Madonna finished her race in 16:32:00 minutes beating Hollander's time of 16:45:55 although they competed on different courses. Hollander, Buder, and Bob Scott were 82 when they competed in the 2012 Ironman World Championship in Kona on October 13, 2012, but Buder and Scott did not finish the race.
On October 5, 2010 Sister Madonna released her autobiography, The Grace to Race: The Wisdom and Inspiration of the 80-Year-Old World Champion Triathlete Known as the Iron Nun.
Buder attended the Challenge family Inaugural year in Penticton BC, Canada on August 25, 2013 during the bike portion in a relay team finishing her portion of the Challenge in 7:38:45. At the Volunteer/Athlete Banquet held the next evening Aug. 26, 2013 Felix Walchshofer CEO of Challenge Family Penticton invited Sister Madonna to compete in Challenge Roth next year as a single Triathlete.
In 2014 Buder was inducted into the USA Triathlon Hall of Fame. 
- Hertz, Mark (July 23, 2010). "At 80, the 'Iron Nun' Prepares for Her Next Triathlon". Tonic. Retrieved July 27, 2010.
- "Sister Madonna Buder Sets Ironman Triathlon World Record". Impowerage Magazine. August 28, 2012. Retrieved September 7, 2012.
- "Dave Erickson chats with 'Iron Nun' Sister Madonna Buder about what motivates her at the age of 80". Everymantri.com. October 22, 2010. Retrieved September 7, 2012.
- Neufeld, Kelly (September 10, 2011). "The Iron Nun- Still Going Strong at 80". Impowerage Magazine.
- Neufeld, Kelly (October 17, 2011). "Sister Madonna: The Iron Nun". Impowerage Magazine.
- 2012 "Ironman World Championship Participant List". Retrieved September 4, 2012.