Katie Ledecky called on a source of inspiration close to home as she ended her wait for a gold at the Tokyo Games with victory in the women's 1500m freestyle final.

Ledecky, who Olympic great Micheal Phelps hailed as "the best female swimmer that we have ever seen", had endured a frustrating start to the Games, failing to defend the 200 metre and 400m free golds which she won at Rio 2016.

Australia's Ariarne Titmus has instead enjoyed the breakthrough to stardom this time around, but Ledecky finally struck gold in Tokyo as she powered to glory in the maiden women's 1500m event.

It took her total of Olympic golds to six – the 24-year-old becoming the fourth female swimmer to reach that mark, after compatriots Jenny Thompson (eight) and Amy van Dyken (six), and Germany's Kristin Otto (six).

Ledecky, who clocked in at 15:37.34, is also just the fourth American woman to claim six golds, after Thompson, Van Dyken and Allyson Felix.

Erica Sullivan clinched silver to seal a one-two for Team USA, and Ledekcy revealed her thought process following a disappointing fifth-place finish in the 200m race.

"After the 200, I knew I had to turn the page very quickly and in the warm-down pool I was just thinking of my family," said Ledecky, who has now won gold medals at three different Games, following success in London, at the age of 15, and Rio.

"Each stroke I was thinking of my grandparents. They're the toughest four people I know and that's what helped me get through that.

“It means a lot. People maybe feel bad that I'm not winning everything, but I want people to be more concerned about other things in the world. People are truly suffering. I'm just proud to bring home a gold medal to Team USA.”

Sullivan's silver handed the USA's first one-two finish in a women's swimming race since Sydney 2000, when Brooke Bennett and Diana Munz wrapped up the top prizes in the 400m freestyle.

“I'm so happy to go one-two with Erica," Ledecky added. "It is the first women's 1500m (freestyle in Olympic history) so I couldn’t have a better outcome than that. I’m so, so happy."

Sarah Kohler completed the podium to become the first German swimmer to win an Olympic medal since 2008.