Benji Madden has praised his ''beautiful wife'' Cameron Diaz on her 45th birthday.

The Good Charlotte star has shared a heartfelt social media post insisting he is the ''luckiest guy alive'' because he is married to the Hollywood star, who celebrated her latest milestone on Wednesday (30.08.17).

He shared a picture of the pair on his Instagram account and attached the caption: ''Happy Birthday to my Beautiful Wife I feel like I am the LUCKIEST guy ALIVE I don't think anyone could ever know the Depth, Kindness, and Compassion that I get to experience everyday thanks to My One and Only- You got me til the end baby (sic)''

The image shows the pair embracing while wrapped up in warm clothes while out on a boat.

Benji's post is a rare sign of public affection for the guitarist, who last shared an Instagram shout-out to the blonde beauty in April 2016.

The 38-year-old star praised his ''beautiful and fearless wife'' for releasing a book, 'The Longevity Book', which is about growing older.

He wrote: ''Today is the day! The LONGEVITY BOOK is out! Beautiful&Fearless Wife @camerondiaz set out to Encourage women, and ALL of US to invite a new conversation about Aging, and the privilege of time. I'm so proud My best friend, my Heart, and the most bad ass Chick I know Go get'em baby #luckyman #mywife #bestseller #keepliving #newaging (sic)''

In June, Cameron gushed about Benji - who she married in 2015 - while speaking to her pal Gwyneth Paltrow at the star's Goop health and wellness conference.

She said: ''I think it's a matter of - I just hadn't met my husband, you know? I had boyfriends before. And there's a really, really distinct difference between husbands and boyfriends. And I have a husband who is ... just my partner in life and in everything. Talk about two very different people, we are so different from one another but we share the same values ... we're totally two peas in a pod. We're both just weird enough for each other.''