Olivia Wilde's dog has died.

The 34-year-old actress has been left heartbroken after her canine companion Paco passed away on March 11, just a day after she celebrated her 34th birthday and she, has paid a touching tribute to her furry ''best friend''.

The 'House' actress took to Instagram to post a series of pictures showing times where her lovable pet brought her ''peace''.

She captioned the post: ''Lost my best friend last night. Paco was a kind, wise, gentle, loving soul. I could post a thousand photos of so many adventures. These pics remind me of how peaceful he made me. My heart feels broken right now. All I can ask is that you consider adopting a pup, and loving them with all you've got. Here's to all the incredible friends of Paco who've been so kind to him over the years. I am forever grateful.(sic)''

Paco was Olivia's first adopted dog and just a month ago, the actress posted a picture commemorating their 16 years together.

She captioned the image of her sweet pet: ''Been with this handsome man almost 16 years. What's our secret? Same as most true lovers. Bacon.(sic)''''

Olivia and her partner of eight years, Jason Sudekis - who are parents to son Otis, three, and 17-month-old Daisy - decided to adopt another ''furry son'' in July 2017 and the 'Vinyl' star urged her fans to follow their lead and adopt from animal shelters, rather than shop for pets at a store.

She shared a picture of the dog on Instagram and wrote: ''Ladies and gentlemen, meet the heartbreaker formerly known as Maxamillion, now christened by his new human brother as Elvis Sudeikis-Wilde. 3 years young and 8 lbs of pure goodness. He's lived a pretty harrowing life so far, and we are so lucky he adopted us as his new family, so we can treat him like the king he was born to be. Thanks to @barcshelter we found the missing member of our brood. This is our second adopted furry son and we cannot recommend it enough. There are so many animals looking for homes. This little guy was next on the kill list at a shelter in Texas not too long ago! Please consider saving a dog today.(sic)''