Alistair Brownlee retained his Olympic men's triathlon title to win Britain's 20th gold medal of the Rio Games, with brother Jonny claiming the silver.
Alistair, 28, pulled away from 26-year-old Jonny about halfway through the 10k run in sweltering conditions.
The Yorkshiremen were close throughout the swim, cycle and road race stages, with Alistair walking over the line six seconds ahead.
Henri Schoeman was third, claiming South Africa's first triathlon medal.
Analysis: Inside story of the Brownlees' triumph
Alistair Brownlee is the first athlete to win successive Olympic triathlon titles, while Jonny improved on the bronze medal he won at London 2012.
The brothers were part of a 10-strong group that pulled away during the 40km bike stage, having comfortably negotiated the 1,500m open-water swim from Copacabana Beach.
Mario Mola of Spain, ranked number one in the world after winning four ITU World Series events this year, finished more than a minute behind the Brownlees in eighth.
Britain's other entrant, Gordon Benson, did not complete the race after crashing on the seventh lap of the eight-lap cycle leg.
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