SPEIDI TIES THE KNOT!

Heidi Montag and Spencer Pratt have done the unthinkable: they eloped in private!

The attention-loving Hills stars married in Mexico on Thursday, Nov. 20, according to a report.

The nuptials took place at the One & Only Palmilla Resort, just outside Cabo San Lucas. It appears no family was present for the big event.

We're guessing Heidi's frenemy Lauren Conrad didn't play maid of honor.