Millie Bobby Brown Rocks Skimpy Bathing Suit on European Honeymoon

Millie Bobby Brown's enjoying a European getaway with her new husband ... and, apparently, their honeymoon's a family affair 'cause his legendary dad's right by their side.

The actress hit the beautiful Italian island of Sardinia with her hubby Jake Bongiovi ... and, ya gotta see the pics 'cause she's got a marital glow about her while tanning at their villa.

There's Millie in the bright orange long-sleeve button-down over her one-piece bathing suit -- which didn't cover up much more than a bikini, we should note.

Of course, Jake's hanging out with her in his prep school best -- white sweater vest and matching shorts ... but widen out the frame and there's papa Jon Bon Jovi crashing what otherwise looks like a honeymoon. It can't qualify as such when your dad/father-in-law's there!

Jon's shirtless in the snap ... but, he's got a big smile on his face -- and, Jake and Millie don't seem to care too much that he's hanging with them.

As we told you ... Millie and Jake tied the knot in a secret ceremony last month after several years of dating -- confirmed when they flaunted their wedding rings on a day out in the Hamptons, and then again a couple weeks later when they hit Universal Studios and MBB wore shorts with "Wifey" written on the butt.

The couple was reportedly planning to have a larger wedding ceremony with family and friends ... so, that could be why they're all over in Italy together..