Benji Madden has praised wife Cameron Diaz for being "loyal" and "selfless" in an emotional birthday message.

Benji Madden and Cameron Diaz

Benji Madden and Cameron Diaz

The 37-year-old star wished his significant other a happy 44th birthday by taking to Instagram to post a picture of the couple standing in the Los Angeles County Museum of Art's famed Rain Room and added a heartfelt message, admitting he is a "lucky guy".

He wrote: "Happy Birthday to my beautiful Wife, You're my best friend and I'm so thankful for you, sometimes I just want to tell the world Generous, Kind, Compassionate, Selfless, Humble, Thoughtful, Patient and Loyal. Just a few of the qualities I would use to describe who you are, consistently, everyday. Thanks for being you, I'm a lucky guy Here's to many more I love you@camerondiaz (sic)"

The couple tied the knot last year and Cameron recently admitted she feels proud "everyday" to have Benji as her husband.

She wrote on Instagram: "One of my favorite things about being married, is how much pride I take in my husband

"He makes me proud everyday. One day it might be how generous and giving, another how gentle and thoughtful. Or when he is fiercely protective of the people he loves and cares about.

"Everyday single day I am so incredibly proud of his integrity as a human being. (sic)"

Benji is no stranger to publicly gushing over his wife.

He previously said: "I'm extremely proud of what she uses her platform.

"She's a modern day feminist - she wanted to change the conversation that's being had about women and ageing.

"It's been one of the most inspirational things in my life watching a woman be so courageous ... she's got so much integrity. I'm a lucky guy that I get to experience that."