Ending his campaign with a bang, the European champion won his final two matches by ippon, judo's equivalent of a knockout, over Sergiu Toma of the United Arab Emirates in the semi-final and then American Travis Stevens in the final of the men’s -81kg category.
Russia had also won bronze in judo on Sunday, extending its strong run in the sport after claiming five medals total at the Olympics four years ago, including a London-best three gold.
Khalmurzaev had praise for Stevens and how he pushed him to victory.
“I know this opponent and I know he is strong, so I did all I could do to win this gold medal,” he said.
Khalmurzaev’s triumph ended Stevens’ dream of becoming the first man from the United States to win gold in judo.
Despite settling for silver, it was third time lucky for Stevens after he had come home without a medal from the Beijing and London Olympics.
Takanori Nagase won Japan's sixth judo bronze medal so far in Rio, though his country remains stuck on one gold – a figure that the traditional judo power surely wants to boost.
Toma won the other bronze.
In the women's -63kg category, Slovenia's Tina Trstenjak defeated Clarisse Agbegnenou of France to become her country's second Olympic judo champion.
After breaking Brazilian fans' hearts by topping Mariana Silva in the semi-finals, top seed Trstenjak handily beat Agbegnenou by ippon less than two minutes into the final.
Israel's Yarden Gerbi and Anicka van Emden of the Netherlands won bronze.
Agbegnenou's silver snapped a medal drought for France, seen as a top contender in Rio but which had come up short in the first three days of judo action.
"This medal does not have the right colour, but it is still beautiful,” Agbegnenou said.
"I wanted to open the (French judo) medal count with a nice gold medal but the silver medal is not bad either.”
France is one of just three countries fielding a full team of 14 judokas in Rio and was hoping for a repeat of its strong performance in London four years ago, when it claimed seven medals - tied for the most with Japan.
(Reporting by Chris Gallagher; Editing by Alison Williams and Meredith Mazzilli)
