BARCELONA (REUTERS) - American teenager Katie Ledecky set a world record to win the women's 800 metres freestyle gold medal at the world championships on Saturday and complete a rare treble of distance titles.

The 16-year-old, who smashed the 1,500 metres world best to win gold on Tuesday and also won Sunday's 400 metres, clocked a time of eight minutes 13.86 seconds at the Palau Sant Jordi in Barcelona.

She was inside the previous best of 8:14.10 set by Rebecca Adlington to win gold at the Beijing Olympics in 2008.

It was her fourth title of the week - she also swam in the winning US 4x200 freestyle relay team - and she is only the second woman to win all three distance freestyle titles at a single world championships.

German Hannah Stockbauer won the treble at the 2003 edition, also in Barcelona.

Dane Lotte Friis, who finished second to Ledecky in the 1,500, took 800 silver in 8:16.32 and Lauren Boyle of New Zealand, also third in the 400 and 1,500, won the bronze in a time of 8:18.58.