Ariana Grande is ready to say "I do" again -- this time, she's set to get married to a relatively new lover who's low-key ... but who has clearly stolen her heart.

Ari broke the news Sunday on Instagram with a series of photos of her and BF-turned-fiance Dalton Gomez ... showing off shots of the two of them lying on the floor together, as well as some close-ups of her massive new rock, which she proudly wore on camera.

She captioned her post, "forever n then some." So yes, it looks like AG is gearing up to walk down the aisle once more -- this not too long after she broke off her previous engagement.

Remember, it was just a couple years ago that Ariana and then-fiance Pete Davidson were supposed to get married. They dated for a bit in 2018, and then all of a sudden ... they were engaged. She seemed pretty smitten over PD at the time, but in October ... they called off the engagement amid news that Mac Miller died, plus other circumstances were at play.

Ari's dating life was pretty low-key after that -- but earlier this year, it became increasingly apparent she had a new man -- as she'd been seen hanging with Dalton in recent months ... not to mention smooching him in public, albeit on the DL.

The guy's a young real estate wiz who handles multi-million dollar listings for A-listers in Hollywood. By the looks of the engagement ring he gave her ... dude does very well.

Congrats, Ari ... again!