9 Best Thermal Underwear for Women

9 Best Thermal Underwear for Women

Thermal base layers are the perfect complement to long hours spent outdoors, or a whole day just hanging out your Airbnb. What we’re trying to say is, thermal underwear is crazy comfortable and will keep you feeling cozy wherever you go! Here, we’ve selected nine of the best thermal tops and bottoms for women that’ll check off all the boxes you could hope for. 

9 Best Thermal Underwear for Women

Best overall underwear: Patagonia Capilene® Midweight Bottoms

We’ve ranked Patagonia’s Capilene® Bottoms as best in show because of their classic look and smooth feel that pairs well with all kinds of conditions. This comfortable, sleek design is made from 50 to 100% recycled polyester, giving it an amazing wicking power and unmatched breathability. If you’re in the market for a durable base layer with four season performance — and that won’t put a drain on your wallet — this underwear should definitely be a top contender. 

  • Price range: starting at $69.00
  • Fabric contents: recycled polyester

Best Merino wool underwear: Icebreaker Merino Everyday Base Layer

The truth is, Merino wool is essentially unmatched in its quality and versatility. Not only is this material naturally breathable and odor resistant, but it helps to regulate your body temperature in any and all climates (meaning it can keep you warm *or* cool, depending on your environment). This base layer from Icebreaker does exactly that, plus serves as a performance alternative to synthetic-based apparel, creating a more sustainable future for our planet.

  • Price range: starting at $80.65
  • Fabric contents: Merino wool

Best affordable wool option: Meriwool Merino Thermal Pants

When you want all the luxury of Merino wool thermal wear, but you need to be mindful of your budget, these pants from Meriwool might be just the thing. This midweight underwear provides similar thermoregulation and stretch as that of more expensive options, and comes in a fun range of colors to boot. Fans of this design rave about its ability to dry quickly and insulate well (even when wet), making them a great option for keeping warm on a cold, wintry day. 

  • Price range: starting at $59.99
  • Fabric contents: Merino wool

Best lightweight performance underwear: Odlo Light Crew Neck Top

If you need a thermal top that’s lightweight enough to take with you anywhere, we’d point you in the direction of this crew neck from Odlo. This layer comes equipped with ventilation zones to encourage greater airflow, as well as built-in moisture wicking features to move away sweat as efficiently as possible. Plus, Odlo has made sure you’ll be totally unrestricted in your movement, thanks to flat-lying seams that reduce irritation (caused by rubbing or chafing).

  • Price range: starting at $89.00
  • Fabric contents: polyester, polyamide, elastane

Best silk underwear: Terramar Thermasilk Pointelle Pant

These silk thermals from Terramar are made with 100% silk pointelle knit, giving them optimal warmth while still being super lightweight. The antimicrobial properties in the silk will have you feeling fresh, while the comfort stretch waistband and embedded UPF protection serves up amazing practicality and convenience. And if that wasn’t enough, the flexible rib trim and elegant color selection is sure to bring a sleek presentation to your whole look.

  • Price range: starting at $42.50
  • Fabric contents: filament silk

Best insulated underwear: Arc'teryx Rho LT Bottom 

The Arc'teryx Rho LT is somewhat of a cult favorite, due to its impressive stretch, fleece-lined construction, and versatile fit. This base layer is ideal for low to medium output on chilly days, since the Torrent fleece lining supplies exceptional wicking performance. Reviewers say the thickness (i.e. insulation) is just right to allow for maximum breathability, while also being durable enough to withstand any number of cold weather activities you’ve got lined up. 

  • Price range: starting at $61.99
  • Fabric contents: polyester, elastane

Best synthetic underwear: Hot Chillys Zip-T Base Layer Top

This thermal top from Hot Chillys has been designed with excellent moisture management and odor-blocking properties. Made from 100% polyester, this pick also comes with a handy zipper closure, UPF 40+ protection, and a nice midweight that’ll pack up in a snap. So whether you’re spending a summer night by the beach or enjoying a little getaway in the mountains, this base layer top will make a great companion to whatever kind of adventure you embark on. 

  • Price range: starting at $48.32
  • Fabric contents: polyester

Best splurge-worthy underwear: Smartwool Merino 250 Base Layers

Smartwool is all about bringing comfort to high-performance clothes, which is exactly what these base layers will do. Manufactured from 100% Merino wool fabric with an interlock knit, these thermals offer breathable warmth, help move sweat away from your body, and provide ‘next-to-skin’ comfort while you’re spending time in cold temps. If you’re down to splurge a little, these bottoms make an awesome layer for camping, running, hiking, and more.  

  • Price range: starting at $99.99
  • Fabric contents: Merino wool

Best thermal set: Thermajane Ultra Soft Long Johns Set

Few things are cozier than a long johns set, right? We certainly think so, which is why we’ve included this one from Thermajane on our list! This set combines performance with fashion to give you a totally cute, streamlined look. The form-fitted, four-way stretch fabric actually has a moisture transport system to efficiently wick away sweat; gone are the days of feeling sticky or clammy while you’re lounging around, because here, comfort and dryness are guaranteed.

  • Price range: starting at $26.59
  • Fabric contents: microfiber, spandex

Common FAQs

What is the best thermal underwear for extreme cold?

If you’re traveling somewhere with extremely cold temperatures, Merino wool will likely become your best friend. That’s because wool fibers have a natural crimp that keeps you warm by insulating rather than trapping heat — in other words, the material acts as a buffer against harsh or inclement conditions. Check out Icebreaker or Smartwool for some great Merino options!

What is the most comfortable long underwear?

Silk is a superior fiber for long underwear, seeing as it’s incredibly soft and breathable. In addition, silk fabrics wick moisture away from your skin so you can stay comfortable in a range of climates. Thermals made from silk travel well, too, since they’re anti-static and noticeably lightweight, meaning they can be tossed in any suitcase or carry-on for ease of wear. 

Does thermal underwear keep you warm?

Yes, thermal underwear does an excellent job of keeping you warm (and dry) by regulating your body temperature. With that said, keep in mind that the weight of the fabric itself will largely determine the level of warmth. Still, you can rest assured knowing a lot of lightweight thermals have been designed and/or engineered to provide warmth for hours on end.

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