Lil Wayne's got another one ... not a rap hit ... but another huge athlete for his Young Money APAA Sports & Entertainment Agency, this time signing a champion boxer to the team ... TMZ Sports has learned.

Wayne's new kid ain't some no-name prospect, its Erickson Lubin who's 18-0 and about to fight for the super welterweight championship of the world.

Lubin is fighting champion Jermell Charlo at the Barclays Center on October 14 and recently struck a pose with Young Money president Mack Maine, the guy responsible for bringing him to the team.

This is a huge move into boxing for Young Money, Lubin is a budding superstar and if he beats Charlo -- who's undefeated, too -- could be in line for some HUGE money fights.

Keep your hands up, kid.