Iran Press/ Middle East: Playing with the white pieces, the reigning champion beat Russian challenger Ian Nepomniachtchi in a match lasting 136 moves and nearly eight hours.
"Obviously I'm elated to get this result," Carlsen said in a media conference following the game, which finished after midnight local time.
Carlsen leads the 14-game series 3.5 games to 2.5.
The world champion's victory came after five draws in the championship that has a €2 million prize fund.
The 31-year-old Norwegian has held the world championship title since 2013.
It was the longest game in world championship history, surpassing the previous record of 124 moves set during the 1978 title match between Anatoly Karpov and Viktor Korchnoi.
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