KEVIN DURANT TO JAY-Z YOU'RE MY NEW AGENT Now Go Make Me Millions

Jay-Z is putting Jerry McGuire to shame -- because his budding sports agency just signed three-time NBA all-star Kevin Durant. 

The OKC Thunder superstar just posted an Instagram of he and Jay signing docs that make him Roc Nation Sport's newest client. 

Durant is the latest in a growing list of HUGE athletes jumping ship to Jay's new venture ... like NY Yankee Robinson Cano, NASCAR superstar Dale Earnhardt Jr., and NY Jet Geno Smith 

Durant is Jigga's first NBA star. 

FYI -- Durant is currently in the middle of a massive 5-year, $89 million contract with the Thunder. His move to Roc Nation has more to do with landing big money deals off the court.