America's Sydney McLaughlin smashed her own world record with a sensational run as she claimed Olympic gold in the women's 400m hurdles at the Tokyo Games.

21-year-old McLaughlin, powered down the home straight to finish in 51.46 seconds as she shaved almost half a second off the old mark to reel in compatriot and rival Dalilah Muhammad.

Defending Olympic champion Muhammad, 31, claimed silver in 51.58secs.

The Netherlands' Femke Bol took home the bronze medal behind the reigning world champion.

In a race featuring five personal bests, McLaughlin's blistering time lowered the mark she set at the US trials in June, when she clocked 51.90secs.

After a near 16-year period of the record remaining in tact, Muhammad and McLaughlin have now exchanged the world best on four occasions in the last two years.