The 27-year-old -- the first Norwegian to medal in the triathlon -- crossed the line in a time of 1hr 45min 4sec before raising the tape above his head and then throwing himself to the ground in celebration.
 Jack Yee of Britain took silver 11 seconds behind the winner whilst Hayden Wilde of New Zealand took bronze.
But the main talking point after the race was the chaotic start, which saw around two thirds of the 56 competitors dive into the water and set off on the swimming leg only to be hauled back.
The farcical scenes were caused by a media boat filming the competitors lined up  before diving into the water for the 1.5 kilometre swimming leg.
The pilot of the boat carried on his trajectory oblivious to the fact the siren had gone for the start of the race.
Whilst Yee and others who had been filmed were able to dive in to clear water the triathletes further along were blocked by the
boat, which also reversed dangerously close to athletes already in the water. 
Those able to had begun their race but were recalled once organisers realised the full extent of the disruption.  
It was the first time since triathlon made its Olympic debut in Sydney in 2000 there had been a false start. 
"It's simply remarkable to see that," the announcers said.
Britain had dominated this event in the past two editions through the Brownlee brothers.
However, two-time champion Alistair Brownlee was not selected and his brother Jonathan -- who has previously taken silver and bronze -- finished fifth, 49 seconds off the champion in a race held in trying conditions.
Brownlee had looked a threat as he was part of a group of six approaching the bell for the last of the four running laps.
But his hopes of becoming the first triathlete to win all three types of medals were dashed as Blummenfelt upped the pace at the front.
Yee stayed with Blummenfelt for most of the final lap but the barrel-chested Norwegian had far too much in reserve and pulled away to become the first from his country to medal in the event.    
Organisers prepared for Monday's race by introducing various measures to combat the 27 degree celsius heat (80.6 Fahrenheit) and 75% humidity.
Start times had been moved to earlier in the day to avoid higher temperatures while extra water stations were installed on the running course. Air-conditioning was placed at athletes' areas prior to and post-competition and medical personnel were stationed every 500m along the 10km running course.