From underground hit to global sensation.

Charlotte Awbery went viral last week with a video of a seemingly pitch-perfect performance of Lady Gaga’s “Shallow” captured in a London train station. Now the UK subway singer is proving she’s the real deal — by slaying the Oscar-winning song Wednesday on the “Ellen” show.

“All she was trying to do was catch a train on the London tube and now she has one of the hottest videos on the internet,” says host Ellen DeGeneres, 62, in the new episode.

The camera then dramatically pans to Awbery, 30, impressively nailing the “A Star Is Born” anthem in its entirety onstage, this time with acoustic accompaniment.

Awbery’s meteoric rise has led many to speculate that her viral subway solo was a planned promotional stunt. However, in a post-performance interview with Ellen, the Essex-based cover artist insisted that’s not the case.

“I was literally on my way to meet my friend . . . I’m absolutely overwhelmed by all of this,” Awbery tells DeGeneres of her unexpected stepping stone to stardom.

The singer’s Insta-fame came about when she was prompted by British web personality Kevin Freshwater to “finish the lyrics” to Gaga’s “Shallow.” Suffice to say, Awbery stuck the lyrical landing, causing her to amass almost 300,000 Instagram followers since last week.

However, that wasn’t the singer’s first vocal rodeo. Awbery has previously gone viral on Instagram for her covers of other famous songs, including Judy Garland’s “Over the Rainbow,” Sia’s “Chandelier,” Prince’s “Purple Rain” and Céline Dion’s “Love Is On The Way.”

“My dad’s always said to me: ‘Wherever you are, always sing . . . Never give up,’ ” says Awbery.