AceShowbiz - Dwayne "The Rock" Johnson delighted a sick fan when the star sent the three-year-old boy a clip of himself performing the tune "You're Welcome" from "Moana".

The actor shared the video on Instagram on Monday, November 18, in honour of Hyrum Harris, who is battling Acute Lymphoblastic Leukemia (ALL) - a form of cancer.

Addressing the young fan, the "Baywatch" star said as he spoke into the camera, "Hello Hyrum, I hope this message gets to you."

"You don't know me, my name is Dwayne Johnson, I also go by The Rock and you're probably thinking, 'Of course you by the name of The Rock because you have a head the size of a rock!' "

Joking that he and Hyrum both share a love for the popular Disney flick - in which the actor starred as Maui - he revealed the young boy watches the movie "almost 10 times a day" because his character "gives you strength."

Johnson then sang a few lines from the track "You're Welcome", adding, "I know you're like, 'Dude, leave the cool singing to Maui.' You're absolutely right, Hyrum."

"I wanted to tell you, man, stay strong. There's another dude out there, me, Dwayne, who, like you, loves Maui too. There's no one like Maui. He's the coolest thing," said the "Jumanji: Into the Jungle" star. "I'm a big fan of Maui, too, and I'm a big fan of yours. Thanks for inspiring everyone around you, including myself. Stay strong, Hyrum."

In a subsequent post, Johnson took to the site after Hyrum watched his clip, penning, "Joy and hope cost nothing and yet, is the most powerful gift we can give. Thats the real magic to life. #hopeforhyrum."

It's not the first time Johnson has used social media to reach out to loyal fans - earlier this year, he made a super fan's 100th birthday celebrations extra special when he sent her a personalised congratulations video.