The brunette popstar began her visually impressive performance locked inside a huge gold birdcage before emerging to give us a look at her feathery, bird-inspired, rather weird costume.
How did she sit down or move around?!
Gold was certainly the theme of Katy's performance as in addition to the cage and dress, she opted for metallic make-up that gave her a slightly ethereal, statue-like appearance.
Despite the impressive visual effects and plenty of praise for her appearance, there were grumblings on Twitter about her vocals. Oh dear.
"I don't think Katy Perry will win X Factor," tweeted one viewer. Ouch.
After her performance, she had a brief chat with Dermot O'Leary where she confirmed she'll be kicking off her 2014 world tour in the UK next year.
Interestingly, Katy was sharing the stage tonight with acts including One Direction and, as 1D fans know all too well, she was the one who put Niall Horan through to Boot Camp when she was drafted in as a guest judge during the seventh series.
Needing one more vote to get past his live audition, it was Katy's instinct that he'd go far that saw him heading to Boot Camp. Then judges' houses. Then obviously world domination.
In another Katy nod, the night's finale kicked off with the former X Factor contestants returning to the stage for a group performance of her smash hit 'Roar'. We almost expected Katy to pop up at the end as a surprise but sadly that didn't happen...
Katy performed 'Roar' herself during an X Factor results show earlier this year.
Both 'Roar' and 'Unconditionally' appear on her latest album Prism, which is available now.
Watch Katy's music video for 'Unconditionally' below:
The X Factor final in pictures:
Copyright: Rex Features Tom Dymond / Thames