Young Buck -- I Just Got Evicted!!!

Young Buck is in SERIOUS trouble -- the rapper has been evicted from his Tennessee mansion ... AND the I.R.S is still on his ass for more than $300k in unpaid taxes.

TMZ has learned ... the former G-Unit rapper was ordered to vacate his 5,000 square foot home by May 16th.

The details surrounding the eviction are unclear -- however, court docs show the judge in Buck's bankruptcy case signed off on the sale of the house ... and ordered that the proceeds go towards paying off his massive $333,975.69 debt to Uncle Sam.

Sources tell us ... the rapper -- who bought the house in 2004 -- was spotted earlier this week carrying boxes and removing all of his stuff from the residence.

It's just the latest in a sad series of problems for the rapper ... who filed for bankruptcy back in 2010 ... and was SHOT AT 11 TIMES back in March.