10 Best Long Underwear For Women 2026 in the United States

The Merino.tech Merino Wool Base Layer Women Set is a great choice if you're looking for comfortable, warm long underwear crafted from 100% superfine merino wool. This midweight set (250 g/m²) strikes a nice balance between warmth and breathability, making it suitable for cooler weather activities like hiking or layering in winter. The fabric is soft and fine enough to avoid itchiness, which can be a problem with some wool products. It’s designed to fit well without bunching or rubbing, though sizing and fit can vary slightly by body shape.

One standout feature is its natural moisture-wicking and odor-resistant properties, helping you stay dry and fresh during extended wear. The construction appears thoughtful, but hand washing and flat drying are recommended to maintain softness and shape, which may require a bit more care than synthetic alternatives. The package even includes merino wool hiking socks, adding good value.

If you want a natural, breathable base layer that manages moisture effectively and resists odors, this set is a solid option. For those who prefer machine-washable or lighter-weight base layers for high-intensity activities, exploring other choices might be beneficial.

The Cuddl Duds Thermal Underwear set for women is designed to keep you warm and comfortable during cold weather with its brushed fleece lining and soft outer fabric. Made mostly of polyester with a bit of spandex, this set offers a good stretch that makes it easy to move around without feeling restricted. It’s lightweight at just under 15 ounces, which means it won’t feel bulky when worn as a base layer or even on its own for lounging.

The fit is modern and practical, featuring a thumbhole on the sleeves and a comfortable rise on the leggings, which helps with staying warm and adds convenience. The seams and construction appear smooth and tag-free, reducing chances of irritation during long wear. The fabric is designed to wick moisture away, so you stay dry even if you sweat a little, and it offers breathability to prevent overheating.

Additionally, the material blocks 50+ UV rays, which is a nice bonus if you spend time outdoors in winter. The fabric is mostly synthetic, which might not feel as natural as cotton to some users, and while it helps with moisture, it may not be as breathable as lightweight wool options. For softness, warmth, and ease of movement, the Cuddl Duds thermal set is a solid choice for women looking for a reliable, cozy base layer for cold weather or casual indoor wear.

The Smartwool Women's Classic Thermal Merino Base Layer Bottom is made from 100% merino wool, a natural fiber praised for its softness, breathability, and moisture-wicking abilities. This means it helps keep you dry and comfortable by pulling sweat away from the skin and regulating temperature, which is great for outdoor activities in cold weather. Weighing just 7.2 ounces, these bottoms are lightweight yet warm enough for chilly conditions.

The slim fit design is flattering and allows freedom of movement without feeling bulky, and the mid-rise waist sits comfortably just below the belly button, providing good coverage without being restrictive. Smartwool’s use of flatlock seam construction minimizes chafing, increasing comfort during extended wear. The elastic waistband covered with merino wool adds to the softness against the skin. Additionally, merino wool naturally resists odors, so you can wear the base layer multiple times before needing a wash.

One consideration is that being 100% wool, it might require gentle machine washing to maintain quality and could feel less stretchy compared to blends with synthetic fibers. If you're looking for a sustainable, comfortable, and effective base layer for cold-weather adventures, these pants offer solid performance with a focus on comfort and temperature control.