It's official: The off-the-shoulder trend is sweeping the summer. Fashion insiders like Olivia Palermo have mastered it time and again, and now Kate Middleton has given the style the royal seal of approval too. While at a dinner in London, Middleton chose a sleek white dress by Brazilian label Barbara Casasola, complete with long sleeves and a front zipper detail. While we're sad to report that the dress is currently sold out in the duchess's colour of choice, we did manage to find the exact same dress in black, along with a few pieces inspired by her romantic frock. So, if you're ready to adopt this feminine trend á la Kate, there's no better time. See her full look below, and then shop her style!