Kolak threw a national record of 66.18 metres for glory.
Olympics: Croatia's Sara Kolak wins women's javelin gold
Unheralded Croat Sara Kolak upset the field to win the Olympic Games women's javelin gold medal on Thursday.
South African Sunette Viljoen, a two-time world bronze medallist, claimed silver with 64.92m, while double defending Olympic champion Barbora Spotakova of the Czech Republic took bronze (64.80).
