The billionaire popped the question while sailing around Europe on his new $500 million superyacht, which includes a sexy homage to Lauren, and she said, "Yes." Page Six was first to report the news.

Of course, Lauren's answer should come as no surprise ... the two have been absolutely inseparable since they started dating back in 2019, following Jeff's divorce from his wife of 24 years, MacKenzie.

Jeff looks to have spared no expense on an engagement ring, which Lauren proudly showed off Sunday aboard Jeff's yacht. As you can see, the rock on Lauren's finger is HUGE!!!

Still, no matter what Jeff dropped on an engagement ring, it's just a drop in the bucket to the Amazon founder.

It seems Jeff and Lauren actually got engaged last week, because she was photographed Wednesday with a ring on THAT finger, but it was twisted so the huge rock was hidden on the inside of her hand.

Congrats!!!