The 24-year-old was in stellar form last season, banging in 35 goals, including 20 in the Bundesliga, plus 19 assists in 50 matches in all competitions.
His performances earned him a debut in the France team last March and attracted interest from his former club Paris Saint-Germain and Manchester United.
Nkunku still had two years on his original contract, but Managing Director of RB Leipzig, Oliver Mintzlaff, has secured his services for another four years.
The new deal reportedly includes a significant salary raise with magazine Kicker and German daily Bild claiming a release clause of around €60 million becomes active next summer.
“I was really impressed with the club’s efforts to keep me, so a big thanks to those responsible, especially Oliver Mintzlaff, with whom I was always in close contact,” Nkunku said in a statement.
Red Bull-backed Leipzig won the German Cup last season, a first title for the club which was only founded in 2009 but shot up through Germany’s football pyramid from the fifth tier with four promotions in seven years.
They have again qualified for the Champions League next season and Nkunku said the club has big goals.
“RB Leipzig have made a name for themselves on the international stage in recent years and have shown we can compete for titles,” he said.
“We want to build on that going forward and go one step further.”
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