Benji Madden is a happily married man.

The 36-year-old Good Charlotte rocker wished his new wife Cameron Diaz a happy birthday on Monday by posting an adorable selfie with an even cuter caption.

WATCH: Newlyweds Cameron Diaz and Benji Madden Show Some Serious PDA Courtside

"Happy Birthday to my Beautiful Wife," Madden wrote. "My best friend and Everything else- there's so much I could write. I'm the luckiest guy alive- I get to spend the rest of my life right here. I love this Woman!! Many more Baby!!"

Madden and Diaz got married in January, and the musician has been smitten ever since. In February, Madden got a tattoo of his wife's first name across his chest.

"Thinking bout you," he captioned a pic of the ink. "#LuckyMan."

MORE: Benji Madden Sends Love Messages to Cameron 'Bae' Diaz on Instagram

Diaz has never looked better at age 43, and in an interview with British Vogue in 2010, she shared her salacious secret to staying young.

"The fountain of youth [for me], let's see... I guess it's exercise, healthy diet, lots of water, lots of laughter, lots of sex," she told the magazine. "Yes, sex, we need that as human beings. It's healthy, it's natural, it's what we are here to do!"