The 34-year-old singer is engaged to the Hollywood actor, and the loved-up duo - who split in 2017, before rekindling their romance last year - are ''over the moon'' about the thought of married life.
A source explained: ''Katy and Orlando have been looking forward to this day for a very long time and they are over the moon to embark on their lifetime commitment.
''They talked about an engagement even before their breakup in 2017 but Katy wasn't ready. She just wasn't ready at first but soon after some time away, she knew Orlando was the right man for her life.''
The pop star and Orlando, 42, rekindled their romance in January 2018, and although they've tried to keep their relationship out of the spotlight, they've been planning to tie the knot for ''a very long time''.
The insider said: ''They have been very hush, hush about it but have known for a very long time they wanted to be engaged. They have been preparing for this.''
And, apparently, no one is more excited about their engagement news than Orlando's mother.
The source told 'Entertainment Tonight': ''She has wanted them to tie the knot since the moment she first met Katy. She literally can't stop talking about it, and telling all her friends.''
By contrast, Katy previously claimed she didn't expect to marry again.
The 'Roar' hitmaker - who was married to comedian Russell Brand between 2010 and 2012 - said: ''I'm very pragmatic and logistical and I am less fantastical about things.
''I mean, I was married when I was 25. I'm 34. It was almost 10 years ago. I was like, 'One person for the rest of my life,' and I'm not so sure that that idea is for me. I'm just such a different person than I was.''
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