The aims of the present study were to (1) investigate the participation trends for the origin of athletes competing in 100-km ultra-marathons and (2) determine the nationalities of athletes achieving the fastest 100-km race times worldwide. Race times and nationality from 112,283 athletes (15,204 women and 97,079 men) from 102 countries who completed a 100-km ultra-marathon worldwide between 1998 and 2011 were investigated using single- and multi-level regression analyses. The number of finishers increased exponentially, both for women and men. Most of the finishers (73.5%) were from Europe, in particular, France (30.4%). The number of finishers from Japan, Germany, Italy, Poland and the United States of America increased exponentially during the studied period. For women, runners from Canada became slower while those from Italy became faster over time. For men, runners from Belgium, Canada and Japan became slower. Between 1998 and 2011, the ten best race times were achieved by Japanese runners for both women with 457.1 (s = 28.8) min and men with 393.4 (s = 9.6) min. To summarise, most of the finishers in 100-km ultra-marathons originated from Europe, but the best performances belong to Japanese runners. Although East African runners dominate running up to a marathon, Japanese were the best in 100 km.