Blac Chyna & Alexis Skyy's Fight Was Over Rob Kardashian

When Blac Chyna and Alexis Skyy almost came to blows it was squarely over Rob Kardashian, and a scolding Chyna felt was long overdue ... TMZ has learned.

Sources connected to both women tell us BC did not simply invite Alexis over for a friendly chat during a house party last weekend. Her true goal was setting Alexis straight about her past interactions with Rob ... which Chyna found inappropriate.

We're told Alexis and Rob have known each other since way back in 2016 when he was still with Chyna -- who, we're told, thinks Alexis was a little too friendly with her baby daddy.

Our sources say Chyna wanted to finally clear the air.

Contrary to how Alexis portrayed it on social media, we're told she was the one who started acting wild when Chyna brought up the past -- and that's why BC threw the drink.

Our sources also say Alexis only started barking about a smackdown when her male friend showed up, and they'd been tossed from the party.

Despite the showdown with Chyna -- Alexis and Rob seem to be rekindling whatever they had going on years ago. He's called her his "WCW" and she seems to be totally down.

Hope Rob looks good in referee stripes -- round 2 is coming, we suspect.