The 21-year-old from Groningen finished the final in 53.00 seconds thus breaking the Olympic record, which had been set by her on Wednesday in the semifinals at 53.05.
The silver was taken by Belarusian Aljaksandra Gerasimenja with 53.38 and the bronze medal was claimed by the Chinese swimmer Tang Yi in 53.44.
Kromowidjo was only fourth at the turning point at 0.54 behind Gerasimenja, who turned first. However the Dutch had a strong final sprint and swam to her victory and second medal at London Olympic Games.
On the opening day of the swimming tournament she had won silver medal in the 4×100 freestyle relay team.
“The time was not good!!!” that was Kromowidjojo’s stunning first reaction shortly after her golden race in the Aquatics Centre in London.
“But at the Olympics does not matter,” she added. “I do not think it was a perfect race, but gold is gold,” said the champion.
“I do not know what to say. I’m so happy,” continued the third Dutch winner of the Olympic gold in 100m freestyle. Rie Mastenbroek (1936) and Inge de Bruijn (2000) were the other two Dutch gold medalists before Kromowidjojo. For Ranomi this was her 2nd Olympic title after she had won gold in the 4x100m freestyle in 2008 .