Behdad Salimikordasiabi of Iran won gold in the men's +105kg weightlifting category with a total lift of 455kg.
The world champion entered both stages of the contest late, but comfortably surpassed his rivals.
Fellow Iranian Sajjad Anoushiravani won silver, while Russia's European champion Ruslan Albegov took the bronze medal.
Salimikordasiabi failed a world record attempt of 264kg in the clean and jerk after securing the Olympic title.
The 22-year-old follows in the footsteps of fellow countryman Hossein Rezazadeh, who won this Olympic super heavy title in 2000 and 2004.
"So the world champion becomes the Olympic champion, it is as expected with Iran gold and silver. Once again they have shown what a major force they are in the heavyweight divisions."
Albegov led after the snatch, having posted a lift of 208kg. Salimikordasiabi matched the Russian, but due to his heavier bodyweight he started the second phase of the competition in second place.
Anoushiravani was briefly in the lead when his clean and jerk lift of 245kg gave him a total of 449kg.
However, Salimikordasiabi went back into the gold medal position with his first attempt at 247kg, putting pressure on Albegov.
The Russian would have gone into first place due to his lighter bodyweight had he also lifted 247kg to post the same total as Salimikordasiabi, but he could not steady himself
Anoushiravani then failed when trying to lift 251kg, and Salimikordasiabi was the Olympic champion.
"Coming into this competition my first and most important goal was to get the gold medal, second were the records that come with it. I came here to get the gold medal and I did, in the future I will come on to taking on the record as well," he said.
Earlier, the 2008 champion Matthias Steiner was forced to withdraw with an injury. The German slipped while trying to lift 196kg in the snatch, with the bar falling on to the back of his head and shoulder.
Although not seriously injured, following a medical examination, Steiner did not attempt the clean and jerk.