Miley Cyrus has posted a gushing tribute to Liam Hemsworth to mark his birthday.

The Hollywood stars met on the set of 2010 film The Last Song, and after years of dating on and off, they married in an intimate ceremony in December (18).

While Miley and Liam tend to keep their private lives under wraps, the Malibu hitmaker took to Instagram on Sunday (13Jan19) to celebrate her beau turning 29.

"L, HBD (happy birthday) to my #1... When we met you were 19, Today, you are 29," she began. "I thought I could share some of my favourite things about my favourite dude in honour of this very special day."

Miley then proceeded to list everything she loves about Liam, including how he introduces her to new bands, combs her hair when she is too "lazy" to do so, takes her on long drives and the way in which he paints artwork.

She also described how much she appreciates the way in which he cares for her animals and listens to her problems.

"The way you look at me, the way you look at our dogs... our pigs, our horses, our cats, our fish. The way you look at your family," she wrote. "Your friends... at strangers... at life... the way you look at the ocean and the way you always take your time," the 26-year-old wrote. "The look on your face when you receive good news and how you look AT the bad news. I love how you always try things your way, but are never too proud to ask for help."

Additionally, Miley joked that she even loves his "dirty socks on the floor" and how he helps her do laundry, even if he did once shrink her "favourite" T-shirt.

To conclude the love letter, the star commented, "You and me baby... let's take this dark place head on and shine thru (sic) with the light of L.O.V.E. Thank you for giving me the happiest days of my life. Yours truly, M."

Miley also uploaded a throwback photo to her Instagram page showing her and Liam goofing around the set of The Last Song, with the snap dated 13 July 2009.