The starlet is rarely spotted without a Chelsea girl glow and now she's uncovered one of her favourite ways to get the look.
Millie's current fake tan of choice is Cocoa Brown One Hour Tan, £7.99, a faux glow created by top Irish beauty guru, Marissa Carter.
We've tried countless bronzing buys in our time but there's something pretty spesh about this one.
Unlike most fake tans which require around eight hours to develop, this can be slapped on then washed off in just 60 minutes! After that the colour will stick around for 5 - 7 days.
It's been causing a bit of a buzz in the beauty world after becoming the best-selling fake tan in Ireland and receiving rave reviews since it hit the UK a few months ago.
The former Made in Chelsea star tweeted before and after shots of herself on Sunday (19 January) - tear your eyes away from her ultra-toned legs and washboard stomach and you'll notice a subtle golden hue - with the caption, 'Discovered Cocoa Brown Tan this weekend! Such a gorgeous natural glow in just 60mins. #love #besttan #notorange.'
But Cocoa Brown's not the only tanning brand getting in on the speedy bronzing action.
If you prefer a lotion formula, rather than a mousse, you'll love Montana Tan by Chloe Sims 1 Hour Tanning Lotion, £24.95, which has just hit Boots stores.
Or try Fake Bake 60 Minutes Self-Tan Liquid Mist, £21.20 - a spray-on tan that feels super-lightweight.
Only one hour to develop = less sticky, biscuit-smelling time and more last minute nights out. Hooray!
What's your favourite fake tan? Tell us below as the best comment from across the site each week wins £50!