Ivan Zaborsky

Ivan Zaborsky is a Russian fixed-time, multiday, and backyard ultrarunner from Moscow. At the 2025 GOMU Six-Day World Championship in France, he covered 1,047.554 km, finishing first and exceeding Matthieu Bonne’s ratified IAU world best by 2.035 km.

GOMU and iRunFar called the 2025 performance a world record, but the IAU has not ratified it. As of October 2026, its record list still names Bonne’s 1,045.519 km as the six-day world-best performance and does not show Zaborsky’s mark as pending.

Zaborsky extended his multiday record in 2026. He won the BUFF 72-Hour World Cup with 559.578 km and the Self-Transcendence Ten-Day Race in Moscow with 1,363.763 km. His recognized backyard best is the 106 yards he won with at Biotropika in July 2025, which remains the Russian record on Big’s official table, and he completed 62 yards at Big’s in October 2025. He also reached 121 yards (811.426 km) at Biotropika in June 2026, although the backyard format’s founder said that event’s results would not be recognized. Zaborsky was listed first on the neutral-athlete (AIN) pre-race roster for the 2026 Backyard World Team Championship, which started on October 17.

At that championship he won the AIN race with 81 yards after Dimitrii Romanyuk, the last other AIN runner, did not start yard 81, and he stood out for speed late in the race: his lap was the fastest recorded for its yard on 16 of his 81 yards, including every yard from 67 to 74 and from 77 to 81. On yards 69 and 70 the next-fastest runner was about four minutes slower.