I Think This Is Sienna’s Best Outfit of the Year, and It’s All Down to This Chic Jacket Trend

If my time in the fashion industry has taught me anything, it’s that when Sienna Miller backs something, it won’t be long until it becomes a cult-worthy buy. So this week, as the actor stepped out for one of her many press appearances for her film War, she put me onto a jacket trend I’m now convinced will be everywhere soon.

Stepping away from her usual boho sensibilities, Sienna opted for a sleek, modern look, championing a leather jacket silhouette I think is about to take off. Her cinched-waist style featured strong shoulder pads, a glossy leather finish and a broad collar that borrowed from the traditional biker jacket silhouette.

Styling Balmain’s Signature Leather Jacket (£3590) with the French label’s Low-Waisted Wool Satin Trousers (£1090), Sienna’s all-black look created a sleek, wearable foundation that let the details of each piece shine. The jacket’s cinched waist, for example, created a contoured silhouette, bringing shape and elegance to her otherwise unfussy outfit.

Sienna Miller steps outside in New York wearing a black leather cinched jacket with black bootcut trousers and peep-toe shoes. — (Image credit: Getty Images)

Whilst a black leather jacket will never go out of style, each season tends to bring a fresh take on the classic silhouette. For autumn/winter 2026, oversized proportions, cinched waists and strong shoulders are the details to know.

Having already found a comfortable spot in Sienna’s rotation, I also began spotting the silhouette on a handful of well-dressed editors during London Fashion Week this past weekend. What’s more, key high-street retailers have already started stocking the style, H&M included.

So, if you’re in the market for a new autumn layer, I hope I’ve made a case for this one. Read on to shop the cinched-waist leather jackets I’m recommending below.