Jennifer Aniston Throws Star-Studded Birthday Bash For Fiancé Justin Theroux

It was A-list all the way when Jennifer Aniston hosted a birthday bash for boyfriend Justin Theroux.

The lavish party also introduced the couple's friends to her mansion in L.A.'s Bel Air neighborhood which Jen has spent the last two years renovating.

Guests and the guest-of-honor were all casually attired for the affair which took place on the expansive patio and manicured grounds around the pool.

Ellen DeGeneres and Portia de Rossi, Kristen Bell and Dax Shepherd, Tobey Maguire, Don Cheadle, and Lake Bell were all spotted.

So were Jason Bateman, John Krasinski, Laura Dern and Malin Akerman.

The birthday boy was in jeans -- as were many of the guests -- and Jen wore comfortable shorts for the party that celebrated Justin's 42nd birthday.

It was exactly a year earlier that he proposed.  Jen has said she "already feels married" and is not revealing when they'll actually take the plunge.