Omar Ahmed signed up to run the Bristol 10k race but ended up accidentally running the Bristol half marathon and winning it.
He was eventually disqualified after winning the half marathon in just 63 minutes because he was only meant to run the Bristol 10k.
The Bristol half marathon (22km) was run alongside the 10k race. He went the wrong way when he reached the point where the course diverged for the two distances.
Chris Thompson, of Aldershot, Farnham and District Athletics Club was deemed the winner with a time of 67 minutes after the men’s positions was revised.
The Great Run Company said Mr Ahmed entered the 10k as an elite runner and not the half marathon, therefore he was not officially part of the half marathon race, and would “unfortunately” be disqualified.
It said while Mr Ahmed had put in “an impressive performance”, it had received objections from other athletes and a subsequent investigation took place, resulting in the disqualification.
Paul Foster, chief executive of The Great Run Company, added: “Rules are rules and in this case they say we have to disqualify Omar.
“We salute his performance, and he has been invited to take part in next week’s Great Manchester Run as an elite athlete.
“Of course, we also look forward to welcoming him back to Bristol for 2022’s Great Bristol Run.”
The Bristol 10k is normally held in the spring and the half marathon (22km) is held at the end of the summer, but last year both races were cancelled because of Covid-19.