Lil Wayne celebrates his 40th birthday with YG, Keith Sweat and Skip Bayless

Lil Wayne started celebrating his 40th birthday early...with a star-studded birthday party worthy of the legendary rapper!!!

Sources close to Weezy tell TMZ Hip Hop...that the shindig took place at popular L.A. hot spot The Nice Guy - and several close friends and family members - including his 4 children, flew in from New Orleans for the event.

Special guests ranged from YG and Yella Beezy to Mack Maine and Cortez Bryant on the hip-hop side...and Skip Bayless, Shannon Sharpe and Marcus Wiley represented sports culture.

NBA YoungBoy naturally couldn't be there due to his high-profile house arrest, but sent a video message addressing Wayne as "his son"...because they're both branches of the NBA. Louisiana rap family tree.< /p>

The biggest shocker of the night came courtesy of R&B legend Keith Sweat... who surprised Wayne with a special rendition of his classic track "Don't Stop Your Love".

Wayne's real birthday is Tuesday, when he will receive the royal birthday treatment from the National Museum of African American Music in Nashville. We have learned that they are unveiling a special exhibit in his honor.

NMAAM and Vanderbilt professors will host an event for the exhibit, which will feature antiques personally donated by Wayne, including his best rap album Gramm...