She's one of the biggest pop stars in the world, but it seems Ariana Grande is also a MAJOR fan of Harry Potter!

The US pop-sensation outed herself as Potter superfan when she saved J.K. Rowling from a seriously massive spider. Rowling took to her Twitter account to show her 12.6 million followers the beast she'd caught in her house. Alongside the scary snap she wrote, 'I am a strong, independent woman. Also, thanks very much to my husband for dealing with this so I could go through the door it was blocking.'

Showing her followers she's a true fan, Ariana couldn't resist reminding the author of a useful spell she can use to vanish the spider. Replying to J.K. Rowling's tweet, Ariana wrote, 'arania exumai' [sic].

According to a Harry Potter fan site, 'Arania Exumai' is the incantation of a spell used to blast back acromantulas or other large spiders. If the spell misses and strikes stone, it will produce a large black scorch mark, and thus it is not recommended for use on humans, though casting through or along a human produces no ill effect so long as a spider is struck.

But of course as a HUGE Harry Potter fan...you already know that! ⚡⚡⚡