The pair are engaged after a romantic Valentine’s Day proposal.
The 34-year-old singer took to Instagram this morning to confirm the news after fans shared pictures from her engagement party last night.
"In bloom," she commented, sharing a picture of her pink diamond engagement ring.
Last night fans spotted pictures they say were taken from her mum Mary Hudson’s Facebook page of Katy’s "engagement party" overnight.
Captioned “look who got engaged last night”, the post shows two blurry photos of Katy and Orlando under a heart-shaped arch made of balloons and the pink diamond ‘engagement ring’.
Katy was previously married to Russell Brand from 2010 to 2012, and Orlando was married to Victoria's Secret model Miranda Kerr - who he shares a son with - from 2010 until 2013.
Katy and Orlando have been dating on and off for three years since getting together at a Golden Globes afterparty in 2016.
They split in March 2017, issuing a joint statement saying they were “taking respectful, loving space at this time.”