So - how did the 17-year-old land such a big beauty deal?
"Mac senior artist Amber Dreadon has a longstanding relationship as Lorde's makeup artist, and has designed Lorde's tour looks, as well as her looks at the 2014 Grammy Awards and Brit Awards," says the brand.
Lorde is a fan of Mac's makeup too.
"I have loved Mac Cosmetics since I was a little kid," she said in a statement.
"I remember saving up to buy my very first Mac lipstick [Snob] at 14, and it was used by about 20 of my friends! Mac has a very clear aesthetic, that has always felt fashion forward to me. So I was really excited to work with them on these products, which I use pretty much every day and night. I hope you will too."
Lorde's on a mission to get us all wearing her favourite lipstick. We can't wait to find out what it's called...