A marathon is a foot race that is a little over 26 miles long. The original ancient Greek marathon runner, Phiedippides, actually collapsed as soon as he finished running. The marathon was one of the first Olympic events when the Olympics started in 1896. It was originally 24.55 miles but that has increased to 26.22 and stayed that way ever since 1924. The world's fastest marathon time is two hours, three minutes and 59 seconds.