Jennifer Aniston is off the market again, but this time for good... she's engaged!

Her actor-screenwriter BF Justin Theroux popped the question on his birthday and she said yes!

Aniston met Theroux while working on the comedy 'Wanderlust'.

Jenn & Justin, or should we say, Jennstin have been dating for over a year now, and man this guy must be something. I mean, she did pass on Bradly Cooper, Vince Vaughn and John Mayer.

Good luck on marriage the second time around.

Sorry the first one was the Pitts... haha, get it.