Chad le Clos.
US swimmer Michael Phelps came first, while Russian Evgeny Korotyshkin finished in a dead-heat for shared silver.
Phelps, in his last individual Olympic event, clinched his 17th gold medal, touching in 51.21 seconds.
It was Le Clos's second medal after he snatched gold from Phelps in the 200 metres butterfly final on Tuesday.
– Sapa-AFP