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Men's Underwear

(155 products)

Products (155)

Sort: Best Match

ArtilectFlatiron 185 Base Layer Leggings - Men's
$109.73
Save 31%
compared to $160.00
0 reviews
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
Top Rated
Icebreaker260 ZoneKnit Base Layer Leggings - Men's
$119.73
Save 27%
compared to $165.00
9 reviews with an average rating of 4.8 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Regular, Big
REI OUTLET
StanceInvestor Boxer Briefs - Men's
$22.73
Save 24%
compared to $30.00
3 reviews with an average rating of 4.7 out of 5 stars
Size Type:
Regular, Big
REI OUTLET
StanceSanta Rips Boxer Briefs - Men's
$22.73
Save 35%
compared to $35.00
0 reviews
Size Type:
Regular
REI OUTLET
Top Rated
IcebreakerMerino 260 Tech Thermal Base Layer Leggings With Fly - Men's
$93.73
Save 25%
compared to $125.00
34 reviews with an average rating of 4.8 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Regular, Big
REI OUTLET
StancePalmoflage Boxer Briefs - Men's
$19.73
Save 34%
compared to $30.00
4 reviews with an average rating of 4.5 out of 5 stars
Size Type:
Regular, Big
REI OUTLET
ArtilectFlatiron 185 Crew Base Layer Top - Men's
$96.73 - $109.73
Save 30% - 31%
compared to $140.00 - $160.00
0 reviews
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
StanceWebbed Boxer Briefs - Men's
$19.73
Save 26%
compared to $27.00
0 reviews
Size Type:
Regular
REI OUTLET
Top Rated
Icebreaker200 ZoneKnit Long-Sleeve Crewe Base Layer Thermal Top - Men's
$109.73
Save 26%
compared to $150.00
6 reviews with an average rating of 5.0 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
SmartwoolIntraknit Active Base Layer Crew Shirt - Men's
$81.73
Save 25%
compared to $110.00
1 reviews with an average rating of 4.0 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Big, Regular
REI OUTLET
Top Rated
IcebreakerMerino 260 Tech Long-Sleeve Half-Zip Thermal Base Layer Top - Men's
$99.73
Save 26%
compared to $135.00
34 reviews with an average rating of 4.5 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Regular, Big
REI OUTLET
IcebreakerMerino 260 Tech Long Sleeve Crewe Base Layer Top - Men's
$119.73
Save 27%
compared to $165.00
4 reviews with an average rating of 4.5 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Regular, Big
REI OUTLET
New arrival
Free FlyElevate Boxer Briefs - Men's
$28.73
Save 24%
compared to $38.00
0 reviews
Size Type:
Regular, Big
REI OUTLET
Top Rated
Arc'teryxRho LT Base Layer Hoody - Men's
$96.93
Save 19%
compared to $120.00
46 reviews with an average rating of 5.0 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Big
Icebreaker125 ZoneKnit Merino Thermal Leggings - Men's
$93.73
Save 25%
compared to $125.00
0 reviews
Underwear Weight:
Ultralightweight
Size Type:
Regular, Big
REI OUTLET
New arrival
SmartwoolIntraknit Thermal Merino Base Layer Colorblock Crew - Men's
$97.73
Save 24%
compared to $130.00
11 reviews with an average rating of 4.4 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
SmartwoolIntraknit Thermal Merino Crew Base Layer Top - Men's
$97.73
Save 24%
compared to $130.00
9 reviews with an average rating of 4.1 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
Top Rated
ArtilectDarkhorse 185 Zoned Crew Base Layer Top - Men's
$109.73
Save 31%
compared to $160.00
7 reviews with an average rating of 4.6 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
SaxxRoast Master Midweight Long-Sleeve Crew Base Layer Top - Men's
$52.73
Save 29%
compared to $75.00
0 reviews
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
TerramarC-Suite Mammoth Sherpa Fleece Mid-Layer Pants - Men's
$56.73
Save 29%
compared to $80.00
0 reviews
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
Top Rated
IcebreakerMerino 200 Sonebula Long-Sleeve Crewe Base Layer Top - Men's
$89.73
Save 25%
compared to $120.00
6 reviews with an average rating of 4.5 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
Icebreaker125 ZoneKnit Crewe Base Layer Shirt - Men's
$86.73
Save 24%
compared to $115.00
3 reviews with an average rating of 4.0 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big
REI OUTLET
SaxxRoast Master Midweight Base Layer Bottoms - Men's
$52.73
Save 29%
compared to $75.00
0 reviews
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI OUTLET
Icebreaker200 ZoneKnit Merino Thermal Base Layer Leggings - Men's
$109.73
Save 26%
compared to $150.00
6 reviews with an average rating of 4.2 out of 5 stars
Size Type:
Regular, Big
REI OUTLET
Top Rated
IcebreakerMerino 125 ZoneKnit Long-Sleeve Half-Zip Base Layer Top - Men's
$99.73
Save 26%
compared to $135.00
10 reviews with an average rating of 4.8 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big
REI OUTLET
Top Rated
Icebreaker125 ZoneKnit Merino Long-Sleeve Crewe Thermal Top - Men's
$93.73
Save 25%
compared to $125.00
6 reviews with an average rating of 4.8 out of 5 stars
Underwear Weight:
Ultralightweight
Size Type:
Regular, Big
REI OUTLET
Top Rated
Arc'teryxRho Merino Wool Crew Neck Base Layer Top - Men's
$84.83
Save 29%
compared to $120.00
27 reviews with an average rating of 4.8 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Big, Regular
SmartwoolIntraknit Thermal Merino Colorblock Crew Base Layer Top - Men's
$64.83
Save 50%
compared to $130.00
11 reviews with an average rating of 4.4 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular
Top Rated
Arc'teryxRho Heavyweight Zip-Neck Base Layer Top - Men's
$98.83
Save 29%
compared to $140.00
101 reviews with an average rating of 4.6 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Regular, Big
Arc'teryxRho Merino Wool Base Layer Bottoms - Men's
$96.93
Save 19%
compared to $120.00
4 reviews with an average rating of 3.0 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big

121–150 of 155 products

Sort: Best Match

Related Expert Advice articles

What material is best?

Wool is moisture-wicking and odor-resistant, while synthetic fabrics are more durable and less expensive.

Match the temp to the trek

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

Find your fit

To be able to wick sweat efficiently, your next-to-skin layer needs to actually be next to your skin. A comfortably snug fit everywhere is your goal.

Read full article: How to Choose Base Layers

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