Justin Theroux has wished his ex-wife Jennifer Aniston a happy birthday.

Justin Theroux and Jennifer Aniston

Justin Theroux and Jennifer Aniston

Despite the couple splitting four years ago, the 'Leftovers' star still had a sweet message for his former spouse as he marked her 52nd birthday on Thursday.

Taking to Instagram, he wrote: "Happy birthday @jenniferaniston ... [Love] you B!"

Meanwhile, Justin previously opened up about their "heartbreaking" divorce.

He said: "The good news is that was probably the most - I'm choosing my words really carefully - it was kind of the most gentle separation, in that there was no animosity. Again, neither one of us is dead, neither one of us is looking to throw hatchets at each other. It's more like, it's amicable. It's boring, but, you know, we respected each other enough that it was as painless as it could be.

"It was heartbreaking, only in the sense that the friendship would not be the same, as far as just the day to day. But the friendship is shifting and changing, you know, so that part is something that we're both very proud of."

And Jennifer had been doing "incredibly well" following the split.

A source said of the 'Friends' star at the time: "Jennifer has been doing incredibly well. Her decision to move forward in life without Justin was one of the most difficult of her life but she now knows for sure, it was the right one.

"Since they split, her friends believe their plan to move forward in life without one another was the best decision for both of them. Neither of them is pining for each other but instead, finding themselves again."