The news was confirmed by their rep to Us Weekly.
41-year-old Theroux popped the question Friday night, which also happened to be his birthday.
“Justin Theroux had an amazing birthday on Friday, receiving an extraordinary gift when his girlfriend, Jennifer Aniston, accepted his proposal of marriage,” Theroux’s rep told People.
Theroux works as an actor and screenwriter.
The couple starting dating after they worked together on the movie Wanderlust, but according to CBS News, they have known each other for years.
“Though that film disappeared quickly from movie theaters after its release earlier this year, the relationship clearly proved to have more staying power,” said CBS News. “The two moved in together and tabloids soon began predicting everything from marriage to babies for the new couple.”
Just a few days ago, ABC News reported that the relationship might be on the rocks. Star Magazine had reported that Theroux was spotted with another blonde, and Aniston had broken up with him. But this obviously couldn’t be further from the truth.
“It’s once again just another fabrication to sell magazines and has no relationship to reality,” Aniston’s rep told ABC.
In June the couple embarked on a romantic European vacation, and just last week Theroux visited Aniston in North Carolina on the set of her new movie We’re the Millers.
This will be Theroux’s first marriage, but a second for Aniston, who was married to Brad Pitt from 2000 to 2005.
There is no word on how Theroux proposed, and the couple has not yet announced a wedding date.