Lauren London is NOT pregnant contrary to a rumor that's running amok ... TMZ has learned.

Sources close to the situation tell TMZ ... there is no truth to a report from a weekly L.A. outlet "confirming" Nipsey Hussle's widow is pregnant.

That's backed up by J Roc, a close family friend who was also Nipsey's bodyguard, who is also shooting down the story -- calling it "fake news" -- and calling out those spreading the rumor.

Lauren has 2 children ... including Nipsey's son, Kross Ermias Asghedom.

The rumors, btw, started spreading after the L.A. Sentinel News -- which is headquartered in Nipsey's Crenshaw neighborhood -- claimed it "confirmed" Lauren was about to announce her pregnancy.

But, again ... our sources say it's just not true.

As for J Roc's social media reference to "What It Feel Like" -- that's the new track pairing Nipsey and Jay-Z for the first time. It's on the soundtrack to the new film "Judas and the Black Messiah," and drops later this week.