Bindi Irwin couldn't help but gush about boyfriend Chandler Powell on his 21st birthday.

The 19-year-old Australian television personality dedicated a sweet post to Powell, whom she called "the love of [her] life," on his birthday Monday.

"Happy Birthday to my friend, my team mate and the love of my life @ChandlerPowell," Irwin captioned a photo of herself with the American wakeboarder. "Words will always fall short in describing how much you mean to me."

"Your caring heart and strength inspires me every day," she said.

"I love your strength during challenging times. I love your kindness towards every person and animal you meet. I love you because of a thousand reasons that I could spend a lifetime counting."

"I am beyond thankful that we met on that November day in 2013," the star added.

"I can't wait for more adventures today, celebrating your 21st birthday together. Let's go hike a mountain! You are my sunshine."

Irwin and Powell appeared to spend the day at the Australia Zoo with Irwin's mom, Terri Irwin, and brother, Robert Irwin.

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Powell thanked Irwin and her family for the "special" celebration in a post on his own account.

"Overwhelmed with birthday celebrations today!" he wrote.

"Thank you Terri, @bindisueirwin & @robertirwinphotography for making this day so special already. And it's still only 9:30am! You guys mean the world to me."

Irwin, the daughter of late Crocodile Hunter star Steve Irwin, has previously referred to Powell as "living sunshine."

The couple dressed as Clark Kent, aka Superman, and Lois Lane for Halloween in October.