Britney Spears hits back at Katy Perry's GRAMMYs shade

Game on!

After Katy Perry not-so-subtly took aim at Britney Spears for her 2007 shaved head incident at the GRAMMYs on Sunday, OG pop princess has finally hit back -- and her response is epic!

The 35-year-old singer took to Twitter to share a very telling bible verse: "Her mouth speaks from that which fills her heart Luke 6:45."

This tweet sent her fans in a tizzy, causing many to believe she's throwing major shade at her brunette counterpart.

At the GRAMMYs, Perry revealed that she had been "taking care of [her] mental health," during her almost four-year break from music.

She then told E!'s Ryan Seacrest, "At least I haven't shaved my head yet!"

The quick quip was a clear reference to Spears' infamous head-shaving incident from 2007, which was perhaps the singer's lowest point as she struggled with alleged mental health issues.

Twitter came quickly came to Brit's defense. One fan blasted Katy, saying the remark was "not cute." Another user posted a similar message, writing she's "not down with that."

Britney just made one thing loud and clear: You're messing with the wrong girl, Katy!

The star, who got her start on Disney's "Mickey Mouse Club," is clearly living her best life right now. She skipped the 2017 GRAMMYs for a more intimate affair -- spending time at a lavish Malibu mansion with her boyfriend Sam Asghari. She posted a snapshot of herself lying near an infinity pool on Sunday. The night before, she hit up Clive Davis' legendary pre-GRAMMYs bash wearing a see-through mini dress that showed off her perfect figure.