Alaskan teenager Lydia Jacoby upstaged her 2016 Olympic champion team mate Lily King to win a surprise gold medal in the women's 100m breaststroke on Tuesday.

Lydia Jacoby in sheer joy after her win (Credit: Reuters)

Tokyo:

The 17-year-old pipped Tatjana Schoenmaker to gold, touching in a time of 1:04.95 with the South African 0.27 behind and King in the bronze medal position in 1:05.54.

Jacoby accelerated over the final 25 metres to push ahead of her two rivals, who had been expected to battle it out for gold.

King, 24, currently holds the world record for the event with a time of 1:04.13.

Jacoby, whose parents are both boat captains, started swimming aged six and initially took lessons as a child because of the amount of time her family spent on the water.

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