As the new American Idol judge turned 33 today, an exciting new chapter in her friendship with the former One Direction member began.
In honor of his friend's birthday, the "Slow Hands" singer took to Twitter to wish "the loveliest lady" a happy birthday and a good day, before saying "I love you."
Before you ask yourself, 'Where did this come from,' we're here to explain it all.
The two's friendship was forged when Niall first auditioned for the X-Factor back in 2010—where Katy was a judge—and Katy made the deciding vote that allowed him to continue on to the next round.
Since his subsequent rise to fame, the stars have remained close and continued to cross paths due to their popularity in the music world. In fact, these two have built a friendship that fans simply can't get enough of.
To see the timeline of their friendship and flirtatious encounters check out the photos below!
Photo by Kevin Winter/Getty Images
Niall Horan stole a kiss from Katy Perry... and he liked it! Following the on-stage smooch, Niall spoke in a daze about the glorious moment, saying, "I don't think there will ever be anything cooler than kissing her... until I marry her, maybe."
While walking the red carpet at the 2014 ARIA Music Awards in Australia, Katy supported her friend and even photobombed the One Direction members.
The One Direction pop star cheekily captioned his photo, "She said yes," but not in the way you think! While they are unfortunately not getting married, she did technically say yes to Niall when he first auditioned for The X Factor on which she was a judge, back in 2010.
Article continues below
Niall's slow hands are all over "his lovely wife" Katy in this group photo with their future "groomsmen." Are we the only ones hearing wedding bells?
Darren Leigh Roberts/Newspix/Getty Images
The two singers performed at the finale for Australia's The Voice and were able to spend some koalaty time together down under.
Contrary to fans wishes, Katy Perry has made it clear that the two are just friends. "He's always trying to like, get my number, to like, maybe flirt with me but I'm like, 'I could babysit you. I'm like your mom!,'" she joked.
Article continues below
Getty Images/Dave Hogan for One Love Manchester
Along with a handful of other performers, the two pals joined together to raise money for the One Love Manchester Benefit Concert hosted by Ariana Grande.
Despite the fact that Katy totally friend zoned our boy Niall, there is nothing but love between the two, with the former One Direction star recently tweeting, "Happy birthday to the loveliest lady @katyperry. have a good day, love you!"
Catch the latest news on E! News weekdays at 12PM, 7PM & 11PM in the UK, only on E!