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Underwear

(400 products)

Products (400)

Sort: Best Match

SmartwoolIntraknit Thermal Merino Crew Base Layer Top - Women's
$96.73
Save 25%
compared to $130.00
130 reviews with an average rating of 4.2 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular
REI OUTLET
Top Rated
Arc'teryxRho Hybrid Insulated Base Layer Bottoms - Women's
$99.83
Save 44%
compared to $180.00
17 reviews with an average rating of 4.7 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Regular
Top Rated
IcebreakerMerino 260 Tech Long-Sleeve Half-Zip Thermal Base Layer Top - Women's
$89.73
Save 33%
compared to $135.00
37 reviews with an average rating of 4.6 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Plus
REI OUTLET
Top Rated
Arc'teryxRho Base Layer Hoody - Women's
$95.73
Save 20%
compared to $120.00
25 reviews with an average rating of 4.9 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular
REI OUTLET
Icebreaker125 ZoneKnit Long-Sleeve Crewe Base Layer Thermal Top - Women's
$93.73
Save 25%
compared to $125.00
10 reviews with an average rating of 4.1 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular
REI OUTLET
tasc PerformanceElevation Merino T-Shirt - Men's
$46.73 - $54.73
Save 30% - 40%
compared to $79.00
56 reviews with an average rating of 4.4 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Big, Regular
REI OUTLET
Icebreaker200 Oasis Base Layer Leggings - Kids'
$29.83
Save 50%
compared to $60.00
10 reviews with an average rating of 4.3 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular
IcebreakerMerino 200 ZoneKnit Long-Sleeve Half-Zip Base Layer Top - Men's
$95.83
Save 40%
compared to $160.00
1 reviews with an average rating of 5.0 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
Top Rated
REI Co-opMidweight Base Layer Crew Top - Toddlers'
$17.93
Save 28%
compared to $24.95
16 reviews with an average rating of 4.8 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular
Icebreaker125 ZoneKnit Crewe Base Layer Shirt - Women's
$84.73
Save 26%
compared to $115.00
1 reviews with an average rating of 5.0 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular
REI OUTLET
Top Rated
SmartwoolClassic All Season Merino Long-Sleeve Base Layer Top - Men's
$66.73
Save 25%
compared to $90.00
106 reviews with an average rating of 4.6 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular
REI OUTLET
Arms of Andes300 Alpaca Wool Long-Sleeve Crew Base Layer Top - Men's
$49.83
Save 61% - 64%
compared to $130.00 - $140.00
13 reviews with an average rating of 3.8 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big
Top Rated
IcebreakerMerino 200 ZoneKnit Long-Sleeve Half-Zip Base Layer Top - Men's
$119.73
Save 25%
compared to $160.00
8 reviews with an average rating of 4.5 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular
REI OUTLET
Arms of Andes300 Lightweight Alpaca Wool Half-Zip Base Layer Top - Women's
$39.83
Save 70%
compared to $135.00
13 reviews with an average rating of 4.2 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular
Arms of Andes300 Lightweight Alpaca Wool Half-Zip Base Layer Top - Men's
$49.83
Save 65%
compared to $145.00
17 reviews with an average rating of 3.9 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Big
Arc'teryxRho LT Base Layer Bottoms - Men's
$79.73
Save 20%
compared to $100.00
11 reviews with an average rating of 3.9 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Big
REI OUTLET
Arc'teryxRho Base Layer Bottoms - Women's
$73.73
Save 26%
compared to $100.00
15 reviews with an average rating of 4.2 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular
REI OUTLET
TerramarC-Suite Mammoth Sherpa Fleece Mid-Layer Pants - Men's
$56.73
Save 29%
compared to $80.00
2 reviews with an average rating of 3.0 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
SmartwoolIntraknit Merino 3/4 Base Layer Bottoms - Women's
$89.73
Save 25%
compared to $120.00
0 reviews
Underwear Weight:
Midweight
Size Type:
Regular
REI OUTLET
SmartwoolIntraknit Thermal Merino Base Layer Hoodie - Men's
$134.73
Save 25%
compared to $180.00
2 reviews with an average rating of 5.0 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
The North FaceDotKnit Thermal Base Layer Set - Kids'
$51.73
Save 26%
compared to $70.00
0 reviews
Underwear Weight:
Midweight
Size Type:
Regular
REI OUTLET
Black DiamondCoefficient LT One Piece Base Layer - Men's
$149.73
Save 31%
compared to $219.00
10 reviews with an average rating of 3.3 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular
REI OUTLET
SmartwoolClassic Thermal Merino Colorblock Crew Base Layer Top - Men's
$96.73
Save 25%
compared to $130.00
2 reviews with an average rating of 5.0 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
Wild RyeBassett LITE Raglan Base Layer Top - Women's
$29.83
Save 69%
compared to $99.00
2 reviews with an average rating of 5.0 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Plus
Top Rated
Arc'teryxKyanite Base Layer Bottoms - Women's
$69.83
Save 41%
compared to $120.00
30 reviews with an average rating of 4.7 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Plus, Regular
Kari TraaLucie Base Layer Pants - Women's
$55.73
Save 30%
compared to $80.00
6 reviews with an average rating of 4.2 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular
REI OUTLET
Top Rated
Arc'teryxRho Zip-Neck Base Layer Top - Women's
$120.00
52 reviews with an average rating of 4.8 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Plus
Arc'teryxIonia Merino Wool Base Layer Top - Men's
$90.00
50 reviews with an average rating of 4.4 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
Arc'teryxLana Merino Wool Base Layer Tank Top - Women's
$80.00
4 reviews with an average rating of 5.0 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular
Top Rated
Arc'teryxRho Insulated 3/4 Base Layer Bottoms - Men's
$159.73
Save 20%
compared to $200.00
13 reviews with an average rating of 4.6 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Big, Regular
REI OUTLET

301–330 of 400 products

Sort: Best Match

Related Expert Advice articles

Fabrics

Synthetic: moisture-wicking, quick drying, durable, but can hold on to odor
Wool: moisture-wicking, odor-resistant, cooling in warm weather, can be less durable

Styles

Bikini: less rear coverage, thinner waistband, higher-cut leg
Briefs (women's): full-cut briefs offer more coverage in front and back; hipsters offer medium front coverage and back with higher rise
Briefs (men's): close fit and good support, but less thigh coverage
Boxer brief or boy shorts: snug fit, good coverage, longer cut extends down to the upper thigh
Boxers: looser fit, added coverage can prevent chafing but prone to bunching
Thongs: lightweight and quick-drying but provide the least coverage
Sports bras: compression and support during high-output activities like hiking and running

Read full article: How to Choose Hiking Underwear

Which material is best?

Wool: highly moisture-wicking and odor-resistant
Synthetic: durable and less expensive
Silk: soft and lightweight for casual activities

Match the temp to the trek

Lightweight layers: best for moderate to cool temperatures
Midweight layers: best for cold temperatures
Heavyweight layers: best for below-freezing temperatures

Find your fit

Must be close to skin to efficiently wick sweat; should fit comfortably snug
Base layer is for moisture control; your mid layer is for warmth

Read full article: How to Choose Base Layers

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