The 22-year-old hauled a snatch of 208kg and a clean and jerk of 247kg to set up a dramatic victory with 455kg at the Weightlifting competition at ExCeL.
Salimi's gold adds the Olympic title to the world crown he claimed in Paris last November, where he also pushed other world champions into second place.
Silver went to Sajjad Anoushiravani Hamlabad after a snatch of 204kg, a clean and jerk of 245kg and a total of 449kg.
Russia's Ruslan Albegov, who could have really piled the pressure on Salimi, took Bronze with a total of 448kg.
Such was the dominance of the leading duo who claimed Olympic gold and silver for one country, an unprecedented event in recent Olympics.
Iran's weightlifters Navab Nasirshelal and Kianoosh Rostami had also earlier earned silver and bronze medals in the London Games, respectively.
Salimi's medal was Iran's fourth gold in 2012 Olympic Games in London.