The One Direction hunk took to his Instagram account to post a picture of himself and the 'Roar' hitmaker - who is dating John Mayer - and quipped she had accepted his marriage proposal.
He wrote: ''she said yes ! It's happening! Haha (sic)''
The picture sees Katy with her arm draped over the 20-year-old Irish star in a loving way after they met up in Tokyo.
Niall is in the Japanese city ahead of the final two shows on the group's huge 100-date 'Take Me Home' world tour, while the 29-year-old brunette is promoting her latest single 'Roar'.
Earlier this month, he tweeted: ''I love you @katyperry ! Thank you! Ps . Will u marry me? (sic)''
It's not the first time the pair have shown off some chemistry as they shared a kiss at the MTV Video Music Awards in 2012 after Katy had presented the boy band with the Best Pop Video prize for their hit 'What Makes You Beautiful'.
Following their embrace, Niall said: ''It was amazing and very purple - she had purple lipstick on. I don't think there will ever be anything cooler than kissing her... until I marry her, maybe.''
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