The singer shared an IG vid of this bucket-list moment from her Sardinian escape Monday ... featuring Orlando revving her up as they perch on the helicopter’s edge -- before taking the terrifying leap while clutching hands.

KP also shared two epic pics of them mid-jump -- one capturing the thrill up close ... the other one taken from afar, showing them letting go of each other during the dramatic jump that looks like it was at least 20 feet up.

Now, the helicopter wasn’t exactly sky-high, but it was just enough to give the daring duo a serious adrenaline kick.

Katy didn't miss the opportunity to plug her new track "Lifetimes" ... she dropped some of its lyrics in the post's caption -- "Like the stars are in the sky. You and I will find each other. In every single life."

Thrill-seeking seems to be a priority for Orlando on this vacay -- they're hanging with Jeff Bezos and fiancée Lauren Sanchez, who was piloting the chopper last week when OB went skydiving.

Btw, you can see Bezos' mega-yacht, the Koru, in the background as Katy and Orlando got ready to jump ... and they landed right near the bow.