Sylvester Stallone -- I Got SCREWED By a Con Man ... Thanks to Lisa Vanderpump

Sylvester Stallone claims he was victimized by an "incompetent con man" who bilked him out of $1.4 million in a "shameful" home repair scheme ... and Sly claims he never would have gotten involved with the guy if it wasn't for Lisa Vanderpump.

Stallone has declared legal war on a Mohamed Hadid -- claiming the guy is an "unscrupulous, unlicensed predator" posing as a qualified general contractor.

In his lawsuit, filed today in L.A. County Superior Court by legal pit bull Marty Singer, Stallone claims he hired Hadid to perform high-quality work on his L.A. mansion in 2009 ... after receiving a glowing recommendation from "Real Housewives of Beverly Hills" star Lisa Vanderpump.

Instead, Stallone claims, he was left with "inexpensive, damaged deteriorating and uneven cabinetry and malfunctioning appliances" ... among other things.

Stallone claims Hadid charged him more than $10k for a "high quality wooden kitchen island" ... but instead he installed a "cheap wood veneer/plywood product that is defective and virtually worthless."

Stallone says Hadid also installed an inoperable and unsafe fire pit, an incomplete and unsafe air conditioning system ... and he claims the glass work on the house also sucked.

"Far from the top quality job promised, Hadid's work was riddled with defects, abysmal quality and poor workmanship."

Now, Stallone wants all of his money back ... plus damages ... and warns, "If you want to hire an incompetent con man to do construction, then Mohamed Hadid is your man."