Jennifer Aniston is engaged

Jennifer Aniston is set to wed her actor-screenwriter boyfriend Justin Theroux, it emerged over the weekend.

Theroux popped the question during his 41st birthday celebrations on Friday.

"Justin Theroux had an amazing birthday on Friday, receiving an extraordinary gift when his girlfriend, Jennifer Aniston, accepted his proposal of marriage," a rep confirmed to People magazine.

The couple, who co-starred in 2012 comedy Wanderlust, have been dating for 18 months.

It will be Rock of Ages writer Theroux's first marriage and the second for Aniston, 43. Her first marriage to Brad Pitt ended in divorce in 2005.

Aniston's love life has been the subject of intense scrutiny ever since; her previous boyfriends included rocker John Mayer and fellow actor Vince Vaughn.

"I'm very happy. I'm extremely lucky, and I'm extremely happy," the former Friends star said in an interview on Good Morning America, a few months after she started dating Theroux.

There's no word on a wedding date yet. Aniston's ex-husband Pitt is also set to marry his long-term partner, Angelina Jolie, after getting engaged in April.