The Qatari, whose 2.43m best is the second-highest in history after Cuban Javier Sotomayor's 2.45 set 24 years ago, has won silver and bronze at the last two Olympics and silver in the 2013 World Championships.
But he was a class apart on Sunday, having qualified without a fail he went through the final never looking remotely close to dislodging the bar as he flexed his body into biology-defying shapes.
With the gold secured he went agonisingly close to clearing 2.40 but there was no disappointment and the 26-year-old can target a crack at the world record on home soil when Doha hosts the next World Championships in 2019.
Russian Danil Lysenko, competing as a neutral athlete, took silver with 2.32m while Majd Eddin Ghazal of Syria had the best record of three men who cleared 2.29 to take bronze - his country's first world championship medal for a man.
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"My first big world championships gold and I was so determined to win it," Barshim said. "I was expecting it tonight so I am glad I managed to fulfil my target.
"Let's say, I was recovering last year. I did not want to put too much pressure on myself but now I am back in shape and feel I can go even higher. I do not want to retire one day with the feeling that there is still something left."
Lysenko revealed that he had injured nerves in his lead leg a week before the championships.
"It was very painful even in qualification but especially during my warm-up tonight," he said.
"I even wanted to refuse to continue in the final but after my first attempt at 2.20m I decided that I could do something special. I was trying not to hurt my leg, so my technique was not brilliant."
Canada's world and Olympic champion Derek Drouin was unable to defend his title in London because of an Achilles injury.
(Editing by Ed Osmond)
