Heidi Montag & Spencer Pratt -- ENGAGED!

Heidi Montag and Spencer Pratt are engaged after dating for just eight months, according to Us Weekly.

On Tuesday, Spencer, 23, and Heidi, 20, were enjoying a relaxing day at the Bacara Resort & Spa in Santa Barbara on Tuesday.

The cute couple splashed around in the pool and got cozy in the jacuzzi, before taking a late lunch in their private cabana.

Later in the evening, Spencer got down on one knee and popped the question to The Hills star with a diamond-encrusted platinum band with a pink stone, which he purchased Monday at Ice at Brentwood Gardens

Said one spywitness, “She said ‘yes.’ She’s over the moon!”

Oh, just 50+ pictures inside of Heidi and Spencer‘s full-on PDA display at the pool…