Jeff Bezos Got Engaged to Lauren Sanchez in Spain

Jeff Bezos clearly timed his big proposal to Lauren Sanchez to align with the maiden voyage of his spectacular superyacht and their grand arrival in the French Riviera ... because shortly after landing in Spain last week, he did the deed!!!

Sources with direct knowledge tell TMZ ... Jeff pulled out the 20-carat sparkler on dry land, somewhere in Spain ... we believe either Ibiza or Mallorca. We're told the proposal was private -- just the 2 of them -- and boy, did they keep a secret for a few days.

Check out our gallery. Sanchezos arrived in Mallorca by private jet on May 15 and that's where they first boarded the ship.

They headed to Ibiza May 17 ... check out the photo -- she has a ring, but it's turned around so you can't see the enormous rock.

Fast forward to May 20, when the yacht pulled into French waters, where they headed to Antibes. This is the now-famous butt-slapping pic with the newly-engaged couple.

From there they headed the next day to Cannes, and this is where we see Lauren with her hand on the railing of the ship. The ring is impossible to miss.

As for why Lauren finally turned the ring so the rock was visible ... the secret was out once their guests arrived ... guests including her ex, Tony Gonzalez.

Sanchezos celebrated Monday night on dry land, looking very much in love and super swanky.

CONGRATS!!!