LeBron James Prepping For NBA Season On Italy Vacation W/ Shirtless Yacht Workout

Not even a romantic vacation in Italy can stop LeBron James from prepping for his 20th NBA season -- the Lakers star was spotted shirtless on a yacht Tuesday pumpin' iron ... and he looked GOOD.

LBJ has been over in Portofino this month with his wife, Savannah, getting in some much-needed R&R -- but he's clearly carved out time to make sure he's still getting ready for the Lakers' upcoming slate of games.

James -- wearing nothing more than a pair of tights -- was seen grabbing dumbbells and going to work on the boat ... getting in squats, rows and more.

James looked chiseled, with his abs popping in the Italian sun -- and he seemed to be loving his sweat sesh too, grooving to music while working on his bod.

Unclear how long James is intending to be overseas -- but he'll have to make his way back fairly soon ... the Lakers open preseason play in just a couple weeks on Oct. 3.