Croatia's best judo athlete won the gold 40 seconds before the end of the match after blocking a choke by her Japanese opponent.
On her way to gold, Matić first defeated Jamaica's Ebony Drysdale Dale, Dutch judoka Hilde Jager and Germany's Miriam Butkereit.
This is Matić's best ever result and the first gold medal ever for Croatia in judo.
Matić (26) will compete at the Olympic Games in Tokyo this year.