Millie Bobby Brown, Jake Bongiovi Celebrate Their Engagement with Party

Millie Bobby Brown and Jake Bongiovi aren't walking down the aisle yet, but they're partying like they are ... going all out commemorate their engagement with family members.

The "Stranger Things" star made sure to snap several photos Thursday with her fiancé, Jake -- Bon Jovi's 21-year-old son -- during the private party. And, the couple couldn't look happier, as they posed in front of a sign reading "Mr and Mrs Bongiovi."

19-year-old Millie donned a bridal lace co-ord set -- and Jake was suited and booted in green.

Hairstylist Pete Burkill shared several photos from the celebration, congratulating the young couple and showing off their hair for the event.

As we reported, Millie announced her engagement back in April ... sharing a photo of Jake hugging her, and flaunting her stunning diamond ring.

She captioned the photo with a quote from Taylor Swift's song "Lovers" -- "I've loved you 3 summers now, honey, I want 'em all."

Jake also shared the special moment on his page, posting photos with the caption, "forever."

Millie and Jake have been together since 2021, after initially connecting on social media.