Using her trademark late kick, Soni won gold in 2min 19.59sec, improving the record of 2:20.00 she posted in the semi-finals on Wednesday.

She became the first Beijing swimming gold medallist to successfully defend a title in London.

"I wasn't trying to focus on records or medals or anything, I just wanted to swim one more race the way I knew I could," Soni said.

"It has been my goal since I was a little girl to swim under 2.20, my coach told me I could be the first woman to swim 2.19 and I have been chasing it ever since and I am just so happy.

"I didn't look (at the turn), tonight I just wanted my hand on the wall and then I looked. I am so happy."

Japan's Satomi Suzuki took silver and Russian Yuliyia Efimova earned bronze.

"I can not describe my feelings, this is my first Olympics and to win two medals is beyond my expectations," said Suzuki, who earned bronze in the 100m breaststroke on Monday.

"I am very surprised. I tried to improve myself and go higher and higher, Rebecca's time is the next target for me to beat now."