Babe Ruth's 500th home run bat has a new owner ... and it came with a price tag of ONE MILLION FREAKIN' DOLLARS!!
TMZ Sports has learned ... the piece of baseball history was scooped up by an unidentified buyer in SCP Auction's huge event on Saturday ... going for a record $1,000,800.
The bat -- used to break the 500-HR mark on August 11, 1929 -- was gifted to longtime friend Jim Rice and has maintained great condition through the years.
BTW -- the stick was authenticated by a bat expert, so you know it's the real deal.