Abebe Bikila was selected late to run for Ethiopia in the Olympic marathon in Rome. As he was a late selection the teams sponsor, Adidas, had run out of shoes in his size. So, on 10 September 1960, he ran barefoot and won the gold medal. He then went on to win the 1964 Olympic marathon in Tokyo, this time wearing running shoes. Abebe Bikila ran faster in 1964 when wearing the running shoes.
His achievements are held up as evidence that you can run a marathon barefoot. Critics do point out that he ran faster wearing running shoes. I guess ones perspective on this depend on your own preconceived biases.