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Long underwear, base layers and merino briefs

Women's merino underwear — long underwear and briefs

The layer against your skin, the one that makes all the difference: our merino wool underwear keeps you warm, wicks moisture and resists odours, without the itch. Long underwear (base layer), thermal bottoms and merino briefs — find technical underwear for women at Soccer Sport Fitness from Smartwool.

On this page: Long underwear and base layers · Briefs and thongs · Why merino · How to choose · Brands · FAQ

Long underwear and base layers

Merino long underwear wears right against the skin, under pants or leggings, to keep your legs warm in winter. Light and breathable, it regulates temperature during effort and at rest: perfect for running, skiing and cold days. Several weights (150, 200, 250) for the cold.

Briefs and thongs

For long outings and travel: a merino brief or thong wicks moisture, resists odours over several days and stays comfortable with no seams that rub.

Why merino?

Merino wool naturally regulates temperature (warm without overheating), wicks moisture, resists odours and stays soft on the skin — without the itch of regular wool. The ideal fibre for a base layer.

How to choose

  • Deep cold, skiing: a heavier long underwear (Merino 250 or Intraknit).
  • Running, mid-season: a light base layer (Merino 150).
  • Travel, long outings: an odour-resistant merino brief or thong.
  • Fit: close to the body for an effective base layer.

Our brands

Smartwool, the merino specialist, for running, the outdoors and winter. Layer a mid-layer over it, and round it out with our base layers and our merino socks.

What is long underwear?
It's a base layer for the lower body: a long, fitted undergarment worn right against the skin under pants to keep your legs warm. In merino, it regulates temperature and wicks moisture.

Why merino wool underwear?
Merino regulates temperature, wicks moisture and resists odours remarkably well, even after several days, while staying soft on the skin. Ideal for effort, travel and winter.

Which base-layer weight should I choose?
Merino 150 for running and mid-season, 200 for moderate cold, 250 (or Intraknit thermal) for deep cold and skiing. Choose by temperature and intensity.

Can you wear merino for several days?
Yes: it's one of its biggest strengths. Merino wool resists odours, so you can wear it longer between washes — perfect for travel and expeditions.

How do I care for merino underwear?
Wash cold on a gentle cycle and air-dry. Avoid fabric softener and dryer heat, which damage the fibre. Always follow the care label.