Landon Donovan -- I'M ENGAGED!!!

U.S. soccer legend Landon Donovan has finally popped the question to GF Hannah Bartell ... and SHE SAID YES!

Donovan made the announcement on Facebook ... writing, "I recently got engaged to the love of my life, Hannah. I have never been this happy and I'm excited for our future together!"

As we previously reported, Hannah is a hotel sales exec ... and the two have been dating for more than a year-and-a-half.

Donovan was married once before to a woman named Bianca .. but they divorced in 2011. We're told Landon and Bianca are still "friendly."

We spotted Landon and Hannah on a date back in June together -- looking super happy.

Congrats!