The X Factor stars, who are engaged to be married, were invited to One Direction star Louis Tomlinson's Believe In Magic Cinderella Ball held at the Natural History Museum.
Chloe and Stevi were inseparable on the red carpet and couldn't keep their hands off each other as they posed for photos.
Model and singer Chloe wore a floor-length satin gown with sheer panels and sequinned embellishments. Meanwhile, entertainer Stevi showed off new light brown streaks in his hair.
The dad-of-one couldn't have looked happier as he held Chloe by the waist while they embraced one another.
Stevi and Chloe were joined at the charity ball by fellow X Factor star Ben Haenow, who won last year's series, as well as Louis' bandmate Liam Payne at the charity ball on Monday (10 August).
Stevi and Chloe announced their engagement in July, making them the first X Factor couple to get engaged.
Chloe revealed how she texted X Factor judge Cheryl Fernandez-Versini, who was her mentor on the show, about the happy news and invited her to the wedding.
A few days later, Cheryl accepted the invite by announcing via Twitter that she needed to find a hat.
Stevi revealed on This Morning last month that he and Chloe are planning a summer wedding: "We are thinking next summertime... And yes, I want my daughter as a bridesmaid. I never thought I'd end up with a posh girl! Never in a million years."
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