By TMZ Sports

Huge blow for 50 Cent's boxing company SMS Promotions -- TMZ Sports has learned the rapper's company has just filed for bankruptcy.

50 started SMS Promotions back in 2012 ... and signed some pretty big names in the sport, including then-undefeated champion Yuriorkis Gamboa, James Kirkland and Olympic medalist Andre Dirrell.

But apparently, the boxing biz hasn't been as kind to 50 as it has been to others like his pal Floyd Mayweather ... because according to court docs obtained by TMZ Sports, the company filed for Chapter 11 on May 25th.

In court docs filed in Connecticut, SMS says it has between $100k and $500k in debts.

SMS just put on a fight in Connecticut on May 15th -- though it clearly wasn't enough to turn the company around.