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Jul 01, 2025

Mary-Kate Just Wore Flip-Flops, and This "Dated" Pant Trend | Who What Wear

You'll never guess the pant trend. When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. The Hamptons season has officially started. This means that by

You'll never guess the pant trend.

When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works.

The Hamptons season has officially started. This means that by 2 PM every Friday, New Yorkers begin heading "out East”—to the land of Round Swamp Farm, vibrant hydrangeas, and $75 workout sessions. Leading the fashion scene is Mary-Kate Olsen.

This week, the Bridgehampton resident and co-founder of The Row was seen clutching a brown paper bag and an Amex black card on a grocery run. While Olsen, who’s built her career on her chic style, made the bodega bag look cool, it was her outfit that caught our eye: Free City sweatpants and flip-flops.

On Mary-Kate Olsen: FREECITY Sweatpants ($168); The Row sandals

On anyone else, this combination might seem like a relic from 2006. On Olsen, it was a masterclass in understated luxury combined with nostalgic normcore. She kept her usual loose silhouettes, pairing the sweats with an oversize tee. But the real detail? Those sweatpants weren’t just a random throwback; they were an intentional choice. Free City sweats are actually sold at The Row’s boutiques. In other words, these sweats are less of a “dated” item and more of a wardrobe staple that has the highest badge of honor—Olsen approval.

Then there were the flip-flops. Once confined to pool decks and pedicure chairs, the humble thong sandal has become summer’s most popular footwear trend. On Olsen, paired with loungewear and a nonchalant attitude, it created a look that whispered, “I summer in the Hamptons, but I couldn’t care less if you notice." Feeling inspired to replicate her stylish yet laid-back look this summer? Keep scrolling to shop the best Free City sweatpants and flip-flops.

My go-to black flip-flops. I wore them all over the Hamptons this past weekend.

Style with a white tee, black sandals, and a raffia tote bag.

I'm 90% certain this is the style Mary-Kate was wearing.

The pop of green against the dark pants is so fun.

Fashion people on Instagram live in these sandals.

These with a white button-down shirt would look unexpected but cute.

Chocolate brown leather flip-flops will make any sweatpants look expensive.

This colorway is so pretty.

Senior Fashion Editor Eliza Huber owns these in white and always talks about how comfortable they are.

Love.

Nikki Chwatt is an associate fashion editor based in New York City. She joined Who What Wear in 2024 after writing fashion, beauty, and lifestyle content for WWD, Well+Good, Editorialist, and more. With a passion for personal style and the creativity that comes with it, one of Chwatt's goals is to help others understand that there is no such thing as a “good” or “bad” style; it’s just about putting an outfit together that makes you feel confident in yourself. When she's not writing, you can find her taking a Pilates class, reading a powerful romance novel, or exploring a new wellness spot in Manhattan.

Towel down, SPF on.

They're a dorm bathroom classic.

This is one of the best go-to summer outfits.

Risky but chic.

Spotted on Camila Morrone and Kendall Jenner.

If you're looking for a way to summerify your favorite fancy pants, this is it.

The "just right" shade that feels fresh and elegant for 2025.

Get ready for endless compliments.

It's about time, if you ask me.