Gigi Hadid's Vacation Rental Burglarized in Mykonos

Gigi Hadid has a damn good reason to swear off Mykonos ... the vacay pad where she and her sisters, including Bella, were staying was destroyed by burglars who made off with nearly all their valuables.

Sources with direct knowledge tell TMZ ... Gigi and co. got home one night last week and found the crib ransacked. We're told everyone's stuff was scattered throughout. Well, not the expensive stuff ... since items like jewelry, clothing, purses and sunglasses were all jacked.

We're told they called police, but felt the authorities didn't make it a priority. The girls suspect an inside job, because house staff had access to the house.

The scary incident prompted the group to hightail it outta the island and cut the trip short. We're told they chartered a private plane and headed back home. They had been in Greece celebrating their big sister Alana's bday.

Gigi was definitely pissed, saying ... "Don't let insta fool u. Got robbed. Never going back lol." Not exactly a ringing endorsement for the Greek tourism board.

We got the models' dad, Mohamed Hadid, Friday at Il Pastaio in Bev Hills. As you can imagine, he's just happy his girls are safe.