Paris Hilton Flashes Bare Butt on Italian Yacht Trip

Paris Hilton's embracing the "trophy wife" lifestyle ... branding herself with the label via a new cap -- and backing up the claim by showing off her bod.

The socialite's on vacation near Sardinia, Italy ... and on she posed for an impromptu photo shoot Saturday on the yacht's deck, wearing a tiny multi-colored cover up that, ironically, did little to cover her up.

The low-cut ensemble showed off her chest and the length revealed her bare backside as well.

Paris added a blue hat with "Trophy Wife" written in yellow lettering across it ... and, after seeing these pics, it would be hard for anyone to disagree that she's a prize.

Later on, Paris floated on the water in a smaller craft ... while holding her son, Phoenix -- who wore a life vest as an added measure of safety. Remember, Paris got into some trouble with online agitators a couple years ago when she posted pics of Phoenix sans life vest while on a water-filled day.