Viral Video Of Autistic Boy Joyfully Belting Out 'All I Want For Christmas Is You' Has Mariah Carey Cheering

Mariah Carey's "All I Want for Christmas Is You" is back in the top spot on Billboard's Hot 100 list, but another performance of the holiday favorite has taken the internet by storm.

In a video posted to Instagram, 4th grader Kevin "Knox" Johnson III can be seen belting the tune and spreading Christmas cheer during his school's winter concert.

Knox, who is autistic, joyously sang and danced throughout the number and absolutely killed his solo which garnered cheering and applause from the audience.

His mother Jen White-Johnson who videoed the performance captioned her post:

"Knox's Elementary School Winter concert tonight was everything!"

"He had two back to back concerts today his and his Black Boy Autistic Joy was infectious and on full display!"

"Thanks to all the teachers and staff that prepared the students to give us quite a show!"

"Knox was everything during his solo tonight during the 4th and 5th grade chorus selection of Mariah Carey's '[All] I Want for Christmas Is You.'"

She continued:

"We are blessed that Knox is in a space where he can be unapologetically himself!"

"Schools are meant to be a space of belonging and we all know that isn't always the case for Black Autistic kids in public schools."

"Knox continues to take up space, exuding nothing but joy and kindness to all around him!"

"Knox had such a blast singing his solo that he's been prepping for weeks!"

"Mariah Carey would be proud!! 'All I Want for Christmas Is You' @mariahcarey we love you!"

See her post below to see Knox in action.

WARNING: Video may cause uncontrollable smiling

White-Johnson also posted the full-length video on Twitter.

She captioned it:

"Timeline cleanse if you need one!"

"Knox tonight at his 4th grade school winter concert singing @MariahCarey 'All I Want for Christmas Is You'"

"#AustisticJoy on full display!"

"My kid is everything! I hope Mariah sees this!!"

And, well, she did.

Mariah Carey herself replied in her own retweet of Knox's incredible performance!

Carey exclaimed:

"Your kid IS everything!!!!!!"

"Knox, you made my day. Your JOY gives me and everyone watching JOY."

"THANK YOU for reminding me why I wake up in the morning and do what I do."

"I love you"

She completed the tweet with hearts.

And of course she wasn't alone.

Many others expressed their love of Knox's contagious joy.

White-Johnson told The Washington Post Carey even invited the family to sit front row at her holiday concert at Madison Square Garden in New York City.

Unfortunately, the family wasn't able to attend, but White-Johnson said Carey gave them the "best Christmas present ever."