Top Thermal Underwear Brands for Cozy Comfort

As the colder months approach, investing in high-quality thermal underwear becomes essential for maintaining warmth and comfort. Various brands have earned a reputation for providing top-notch thermal wear that aligns with both style and functionality. From innovative fabric technologies to designs that fit seamlessly under any outfit, these brands cater to a diverse range of preferences and needs. To guide you in making an informed choice, explore the following list of the best thermal underwear brands below.

Illustration of thermal underwear

Best brands of thermal underwear in 2025

Smartwool

Smartwool is a leading producer of thermal underwear, renowned for its high-quality merino wool products that offer excellent thermoregulation, comfort, and durability. Their Classic Thermal Merino Base Layers, previously known as Merino 250s, are highly versatile and suitable for cool to cold weather conditions. These base layers feature 100% merino wool, an interlock knit for enhanced comfort, and flat seam construction to minimize chafing. Smartwool's products are popular among eco-conscious and performance-focused consumers, contributing to the brand's strong presence in the market. The global thermal underwear market, which includes brands like Smartwool, is expected to grow at a CAGR of 3.61% from 2024 to 2031.

Icebreaker

Icebreaker is renowned as one of the top producers of thermal underwear, particularly known for its high-quality merino wool base layers. In 2021, the brand forecasted the sale of over 1.3 million units of 100% merino or plant-based apparel, with 91% of its total fiber composition being merino or plant-based. Icebreaker's commitment to sustainability is evident in its initiatives such as regenerative agriculture, aiming to have all contracted growers join its program by 2023. The brand's merino wool layering system, sourced from New Zealand growers, is highly praised for its comfort and performance. Icebreaker continues to lead in the transition to natural fibers, reducing the use of synthetic materials like elastane, nylon, and polyester.

Patagonia

Patagonia is renowned as one of the top producers of thermal underwear, known for its high-quality, environmentally friendly products. The brand's thermal underwear, often made from materials like Capilene and recycled polyester, is highly regarded for its warmth, comfort, and durability. In the global thermal underwear market, which is expected to grow at a CAGR of 3.71% from 2023 to 2031, Patagonia's innovative styles and materials contribute significantly to the market's expansion. The brand's commitment to sustainability and quality has made it a favorite among consumers, particularly in regions like North America, where the thermal underwear market is most prominent. Patagonia's presence in the market is further bolstered by its wide range of products catering to various consumer needs.

Under Armour

Under Armour, founded in 1996 by Kevin Plank, has established itself as a leading producer of high-performance athletic apparel, including thermal underwear. The company's apparel segment, which includes thermal underwear, generated approximately $3.79 billion in net sales in the fiscal year ended March 31, 2024, making it the company's largest product segment. Under Armour's strong marketing strategies and partnerships with sports personalities like Stephen Curry and Jordan Spieth have significantly contributed to its growth. With global net revenues of about $5.7 billion in 2024 and a workforce of around 15,000 people, Under Armour continues to innovate in styles, hues, and materials, enhancing its thermal underwear product portfolio. This innovation and wide range of products have boosted market demand, particularly in regions like North America.

MERIWOOL

MERIWOOL is a renowned brand in the thermal underwear market, known for its high-quality merino wool products that offer exceptional warmth and comfort. The global thermal underwear market, which includes brands like MERIWOOL, is expected to grow at a CAGR of 3.61% from 2024 to 2031, reaching a market size of USD 10.93 million by 2031. MERIWOOL's products are particularly popular for their moisture-wicking properties and breathability, making them a favorite among outdoor enthusiasts. The brand's focus on innovation in materials and design has contributed significantly to the growth of the thermal underwear market, especially in regions like North America and Europe. With a strong presence in the market, MERIWOOL continues to meet the increasing demand for thermal underwear, driven by factors such as the rising number of working women and the expanding product portfolios of key manufacturers.

Terramar

Terramar is a renowned brand in the thermal underwear market, known for its high-quality and performance-driven products. The brand's Merino Pro series, which combines traditional Merino Wool with innovative knit construction and Climasense technology, offers optimal thermal regulation and comfort. Terramar's Heritage Series and Performance Series are also popular for their warmth and versatility, catering to a wide range of activities and temperatures. As part of a growing market, Terramar benefits from the increasing demand for thermal underwear, with the global market expected to reach USD 11,036.07 million by 2031, growing at a CAGR of 3.71%. Terramar's commitment to encouraging outdoor activities and providing layering solutions that mix and match for perfect body conditions further enhances its reputation. For more information, visit Terramar's official website.

Norrøna

Norrona, a renowned Norwegian outdoor brand, is highly regarded for its high-quality thermal underwear, which combines innovative materials and sleek designs to provide optimal warmth and comfort. Known for its commitment to sustainability, Norrona uses eco-friendly materials and production methods, appealing to the growing number of environmentally conscious consumers. The brand's thermal underwear products are popular among outdoor enthusiasts, with a focus on moisture-wicking fabrics and breathable designs that enhance performance. In the thermal underwear market, which is expected to grow at a CAGR of 3% from 2024 to 2030, brands like Norrona are driving innovation and customer satisfaction.

Helly Hansen

Helly Hansen is renowned as one of the best producers of thermal underwear, leveraging its 140-year Norwegian heritage to create professional-grade gear. The brand's LIFA(r) technology, introduced in 1970, revolutionized the industry with its moisture-managing base layers, keeping wearers warm and dry. Helly Hansen's revenue has seen significant growth, with a 29% increase to $425 million in 2018 and a four-year revenue CAGR of 16% from 2014 to 2018. The company's focus on innovation and brand development has driven its success, particularly in North America and Europe. With over 80% of its revenue generated outside Norway, Helly Hansen has established a strong global presence.

Woolx

Woolx is a prominent brand in the thermal underwear market, known for its high-quality merino wool products that are breathable, moisture-wicking, and odor-resistant. Over the past three months, woolx.com has experienced a 13% growth in revenue, indicating strong consumer demand. Their product range includes base layers, tops, hoodies, and accessories, catering to various activities and weather conditions. In September 2024, woolx.com generated $941,695 in revenue from 6,772 transactions, with an average order value ranging between $125-150. Despite competition, woolx.com excels in conversion rates, highlighting its customer satisfaction and market appeal.

L.L.Bean

L.L.Bean is a prominent brand in the thermal underwear market, known for its high-quality and durable products. The brand benefits from the overall growth of the thermal underwear market, which is expected to reach USD 11,036.07 million by 2031, growing at a CAGR of 3.71% from 2023 to 2031. L.L.Bean's presence in the US market is particularly strong, contributing to the North American segment, which holds the largest share in the global thermal underwear market and is expected to grow at a CAGR of 3.62% during the forecast period. The brand's innovative styles, materials, and wide product range further boost its market demand. As the market sees an increasing preference for thermal underwear among women, L.L.Bean's diverse offerings cater to this growing segment.