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  Hosszu's time of four minutes 26.36 seconds took more than two seconds off the previous best set by China's Shiwen Ye at London 2012.
  Scotland's Hannah Miley, 26, finished fourth after being pipped to bronze by Spain's Mireia Belmonte Garcia.
  Fellow Briton Aimee Willmott, 23, finished seventh.
  Miley, ranked second in the world behind 27-year-old Hosszu, said she had "nothing left" to stop Belmonte overtaking her on the final leg.
  "I could see her. I knew she was coming back at me. I gave everything I had," Miley, who won gold at the 2014 Commonwealth Games, told BBC Sport.
  "It is such a mixture of emotions. I was so close to getting it. It is happy and disappointment all coming together."
  Rebecca Adlington, double Olympic gold-medal winner
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  "I am so angry. I was like, 'Hannah what were you doing?' In the last 50 metres, she did not breathe and look at Belmonte once.
  "If you know someone is coming up, you can give that extra tiny bit if you breathe and think 'she is right there'.
  "I am devastated for her because that was her opportunity. All she had to do was breathe once."
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summary: Hungarian swimmer Katinka Hosszu set a remarkable new world record as Britain missed out on a medal in the women's 400m individual medley at Rio 2016.