Joseph Schooling, a 21-year-old from Singapore, took home the gold with a record time of 50.39 seconds.
Three-quarters of a second later, Phelps touched the wall at the same moment as South Africa's Chad le Clos and Hungary's Laszlo Cseh, all three recording a time of 51.14 seconds.
'It is a wild way to end my individual career. It is just wild,' Phelps said after the race. I was like 'Three? Three of us tied for third?'
But Schooling looked stunned and humbled as he claimed his tiny nation state's first ever Olympic gold medal after racing Phelps, his childhood hero.