The Very Best Women’s Long Underwear
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Long underwear — a.k.a. long johns, thermals, base layers, or whatever else you want to call the cozy, body-hugging tops and bottoms worn beneath looser clothes in cold weather — is my favorite way to keep warm when there’s windchill. Whether you’re walking in the park, or doing something more hard-core like wintercampingorhiking, long underwear traps warm air close to your body and keeps it there. AsAlpine Endeavorsfounder and director Marty Molitoris puts it, “You can have the biggest,puffiest jacketon, but without a good base layer, you’ll still be cold and uncomfortable.”
To find the best women’s long underwear, I consulted outdoor-gear experts, undergarment designers, textile savants, snowboarding stylists, hikers, and campers. Then I tested out those picks for myself. Good base layers should be formfitting — not tight but not loose — in order to retain heat. They are often woven from merino wool or technical synthetic fabrics that also have moisture-wicking and odor-reducing properties. These will come in handy if you’re hiking, skiing or working out in winter: Sweat turns ice-cold when you stop moving around. Yet merino wool and other performance textiles are expensive, and there are cheaper alternatives out there that will better suit those who are simply looking to warm up an urban commute. Our top women’s long-underwear picks for all kinds of activities are below. While you’re here, I’ve also written guides to thebest wool socksandwinter parkas.
Updated on January 14, 2026
We still stand by these women’s-long-underwear picks, which have been updated with the latest pricing and availability.
Our top picks
Whatwe’relookingfor
Materials and construction
When it comes to base layers (and other winter essentials, like wool socks), the experts are unanimous: merino, merino, merino. This natural fiber is one of the best materials for trapping warmth. “My No. 1 recommendation for long underwear is merino wool,” says Sarah Savala, a gear expert and customer-care supervisor at the Seattle-based outdoor retailer Evo. “It wicks moisture away from your body, which also makes the clothing extremely breathable and odor resistant.” On a basic level, it also just keeps you warm (unlike cotton, which holds on to moisture). Merino even offers UV protection — plus, unlike the typical wool, it’s “very soft and feels very nice against your skin,” adds Savala. Instructor of textile science at Fashion Institute of Design and Merchandising in Los Angeles Deborah Young agrees that merino wool has many benefits and is unusually comfortable to wear, with none of the downsides that comes with lambswool. “It’s the softest and finest of the wools,” she says. “It’s not itchy or scratchy, and it’s incredibly fine, so we can make it into incredibly light products — like base layers.” Effective synthetic base layers also exist, and I’ve included a number of non-wool options below, including Patagonia’s recycled polyester Capilene base layers.
Intended use
Because base layers are increasingly technical and specific in their design, I broke down these picks according to activity: whether that’s hiking, skiing, or something more cozy. Base layers for hikers might have thumbholes, while base layers for runners use a mesh weave in order to help expel heat while you’re moving. Skiers might look for not only warmth but stylish colorways and patterns when it comes to their base layers, as well as a zip-collar for ventilation. And you’ll also find recommendations for thin everyday layers that won’t add bulk to your outfit when you head to the office or an outdoor venue.
Weight, comfort and fit
We sometimes think of base layers as tight-fitting and maybe even constricting. But some long underwear is actually so thinly woven that you will barely feel it beneath your regular clothes. Most major outdoor brands tend to offer both lightweight and mid- to heavyweight options, according to season. The heavier the weave, the colder temperatures the base layers can withstand. It goes without saying that heavier fabric will feel somewhat bulkier — but merino wool and some synthetic fabrics can still be both very warm and relatively slim. I took note of how closely each of our recommendations is designed to sit against the skin. Choosing the right fit is a balance between personal preference and what kind of weather you’re facing.
Best women’s long underwear overall
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Materials:Merino wool| Intended use:Everyday| Weight:Light
New Zealand brand Icebreaker is synonymous withall things merino; its sustainably designed apparel is constructed using natural fibers only. So whereas many base layers are woven with nylon and elastic for a bit of stretch, these tops and bottoms are made from pure wool, which means they’re especially good at wicking moisture and retaining body heat. I’ll also note that elastic degrades over time, but wool lasts forever, as long as youkeep it away from moths.
At 200 GSM, these layers are warm without being too constrictive for everyday use. The bottoms are especially good for slipping under a pair of jeans because they have a thinner elastic waistband than other brands. The fit resembles that of boxer-style underwear rather thanyoga pants. I wear these both in the city and when hiking in the mountains; they’re the most versatile of all the base layers on this list.
Best (less-expensive) women’s long underwear
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Materials:Polyester, acrylic, rayon, and spandex |Intended use:Everyday |Weight:Light
Wool and silk base layers are pricey, and cheaper synthetic long underwear will still work — just make sure that you don’t buy anything made of cotton, which dries slowly and doesn’t retain body heat. For everyday urban wear (under your jeans or sweatpants, for example), it’s hard to do better than Uniqlo’s affordable, effective Heattech line. I find these particularly easy to wear around the house, when central heating is doing most of the work but I still want an extra boost of warmth. And they’ve also come in handy while waiting for the Q train in cold and windy subway tunnels. “I love Uniqlo Heattech for layering because it has different warmth levels, it’s breathable, and it’s made of comfortable fabric,” says celebrity stylistKrisana Sotelo. “It’s perfect for those extremely cold winter days. It is also very easy on the wallet.” Iva Pawling, co-founder and CEO of underwear brandRicher Poorer, is also a fan, and ran to purchase a pair during an unexpected freezing-cold NYC trip. “These are super-thin, so they were easy to wear under jeans and saved my built-for-70-degrees self,” she says. (It’s worth noting also that Uniqlo’s soft and drape-y cashmere-blend Heattech turtleneck is worth the $5 upgrade from its completely synthetic T-shirt.)
Best stylish women’s long underwear
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Materials:Polyester, merino, elastic |Intended use:Everyday |Weight:Light
Brooklyn-based Hikerkind makes outdoor clothing that can easily transition to everyday city life. Indeed, I’ve often worn the brand’s merino base-layer tees (which come in attractive tertiary colors and are made from a slightly retro ribbed fabric) as regular tops. Made from a blend of polyester and merino, they’re both office-friendly and comfortable. Crucially, they can be washed much more easily and frequently than pure wool base layers, which can be delicate and definitely require flat-drying. As well as being nice to look at, these tees are also plenty warm, breathable, and odor-resistant. On the turtleneck, you can flip the high collar up or down.
Best silk women’s long underwear
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Materials:Silk |Intended use:Everyday |Weight:Light
As Ira Rosh, divisional merchandise manager at Paragon Sports, explained in our story about thebest base layers for outdoor dining, silk is the thinnest and most lightweight base-layer fabric. (Go for it “if you want to feel like you’re wearing almost nothing underneath,” he says.) Daniel, a sales associate atPanda Sportin Brooklyn, agrees and recommends Terramar for its lightweight and stretchy feel. The leggings and top are made from 100 percent filament silk and are machine washable (although the brand recommends hang drying.)
Best alpaca wool women’s long underwear
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Materials:Alpaca wool, merino wool, tencel |Intended use:Outdoors |Weight:Medium
Peruvian outdoor brand Paka’s ribbed base layers are woven with a blend of royal alpaca wool, merino wool, and Tencel. Alpaca wool is even warmer for its weight than merino, so the idea is that these layers keep you cozy while adding less bulk. Strategist senior writer Lauren Ro has worn the crew top under a jacket when walking her kid to school, and under a fleece and rain coat during an Alaskan cruise. “It’s not too thick,” she says, “and I like that it covers most of my butt.” She adds that the alpaca fibers happen to make these base layers extra soft to the touch.
Best synthetic women’s long underwear
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Materials:Recycled polyester |Intended use:Hiking and everyday |Weight:Mid
When designer Carolyn Yim isn’t wearing the merino leggings she designs forPly–Knits, she swears by Patagonia’s Capilene thermals, which the brand calls its most versatile base-layer bottoms. “Their commitment to responsible sourcing is really neat,” Yim says. “For instance, these thermals are made from 92 percent recycled PET bottles. When you grow out of them, you donate them back to Patagonia’s Common Threads program, which will recycle them again into another new garment. Being able to recycle a garment twice or more is a big deal because it’s hard to keep the fibers stable enough after multiple recycling processes.”Primary Essentialsowner Lauren Snyder agrees: “I like Patagonia thermals because they really do work, and they last. I still have pairs that I’ve had for years.” Other experts — including Molitoris; Rosh; Alyssa Ravasio, founder of the camping booking siteHipcamp; and Daniel Kenney, the public-relations and communications manager at upstate New York ski resortHunter Mountain— all cited Patagonia’s Capilene line as some of their favorite base layers. Being mid-weight, these are suitable for a range of outdoor winter activities.
Best fleece women’s long underwear
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Materials:Polyester| Intended use:Hiking and outdoors| Weight:Heavy
Hot Chillys long underwear is another longtime Strategist favorite. Our former writer Kayla Levyprefers fleecy layersto thin wool or silk ones, citing their warmth and coziness. “They’re more like sweatpants than leggings,” she says. “The initial cold you feel is less than, say, a pair of merino-wool leggings, which do keep you warm but take some time to really heat you up and recycle your body heat.” Although these are a bit bulkier to layer, she adds, they work great under herEverlane carpenter pants.
Best heat-reflecting women’s long underwear
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Materials:Polyester, reflective stretch jersey| Intended use:Hiking and outdoors| Weight:Heavy
Columbia’s futuristic base layers are lined with fabric that reflects your body’s own heat, trapping it in a cozy bubble while still wicking away sweat. Award-winning photographer and travel writer Susan Portnoy, a.k.a.the Insatiable Traveler, fell in “love, love, love” with these layers whenshe wore them on an Alaskan cruise, where they came in handy during glacier hikes. But they’d be perfectly appropriate for battling through chilly city commutes too.
Best mesh women’s long underwear
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Materials:Wool and polyester| Intended use:Hiking and outdoors| Weight:Light
Though their wool-mesh construction may take a little getting used to,designer Stacey Bermantold us that these layers were the best option for staying warm while she worked on a film in the Arctic Circle. She was tipped off to them by her Norwegian colleagues, who have lots of experience with the cold. “The science behind net layers is pretty simple: The open weave of mesh lets your body heat escape as a vapor, instead of sticking close to your body and turning into sweat,” Berman says. “Sweat is the enemy of warmth. With mesh, the heat you produce gets trapped in by the next layer you’re wearing, whether that’s classic long underwear or your clothes.” Though functional enough for extreme Arctic conditions like Berman describes, at 140 GSM, these are also lightweight enough for Brooklyn.
Best women’s long underwear for running
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Materials:Merino, nylon, and polyester |Intended use:Running and sports |Weight:Light
Boston-based running brand Tracksmith has a seal of approval from two of the most dedicated runners on the Strategist’s staff, newsletter editor Ashley Wolfgang and managing editor Kelsie Schrader.Both praise its lightweight Brighton top, which features thicker knit wool on the arms than on the body, as your extremities generally lose heat while running. The top is soft to the touch and, thanks to the merino blend, effectively moisture wicking. Its material is very thin — surprisingly so considering how warm it feels — which makes it ideal for layering under a thicker mid-layer or a windbreaker. And most importantly, adds Schrader: “I find it to be very comfy.”
Best women’s long underwear for hiking
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Materials:Merino wool and nylon |Intended use:Hiking and outdoors |Weight:Light
Ibex’s merino-and-nylon base layers that are lighter, stretchier, and more formfitting than the 100 percent wool ones above — while remaining similarly warm. They’re ideal for hiking and trekking; the nylon weave definitely optimizes movement. Even when I’m staying indoors all day, I can wear the black-and-gray-striped top as a regular long-sleeved tee.It looks like a classic wardrobe basic, but the wool is much better at regulating temperature and wicking away moisture compared to cotton. There’s an optional line of reinforced stitching on each cuff that can be unpicked to turn the sleeves into half-gloves.
Best women’s long underwear for skiing
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Materials:Merino wool |Intended use:Skiing and snowboarding |Weight:Heavy
If you want base layers made by an actual skier, consider Kari Traa, the eponymous line from the three-time Olympic freestyle Norwegian skier who started the brand because she felt there was a lack of choices with style and function for women. This set is made from 100 percent merino wool, with a zip collar for ventilation. The patterns and colorways are beautiful, referencing Nordic ski culture without too much kitsch. I find them to be both very warm and very glamorous: Tra’s matching pieces are so flatteringly formfitting that you will quite literally feel likestupid sexy Flanderson the slopes.
Best women’s long underwear for camping
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Materials:Polyester |Intended use:Camping and lounging |Weight: Heavy
The Dyrtapp co-founder Sarah Smith wears this onesie from cult outdoor company Airblaster while sitting around at base camp on cooler evenings. She recommends it more for lounging around the campfire, “not so much hiking.” The suit’s hood and gloves mean you’re exposing a bare minimum of skin, thus trapping heat and keeping you toasty when you’re not being physically active. Although Smith has the classic Ninja Suit, Airblaster offers an even warmer mid-weight merino-wool option for fall and winter adventures. And to answer your most pressing question: When nature calls (perhaps in the actual wilderness), a 350-degree waist zipper transforms this suit into an almost two-piece.
Some more women’s base layers we’ve written about
Ourexperts
• Daniel Kenney, public-relations and communications manager atHunter Mountain
• Marty Molitoris, founder and director,Alpine Endeavors
• Iva Pawling, co-founder and CEO of underwear brandRicher Poorer
• Alyssa Ravasio, founder,Hipcamp
• Ira Rosh, divisional merchandise manager atParagon Sports
• Kelsie Schrader, managing editor, the Strategist
•Sarah Smith, co-founder,The Dyrt
• Lauren Snyder, owner,Primary Essentials
• Krisana Sotelo,celebrity stylist
• Leigh Wetzel, co-founder,Campendium
• Ashley Wolfgang, newsletter editor, the Strategist
• Carolyn Yim, designer,Ply–Knits
• Deborah Young, instructor of textile science atThe Textile Expert
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