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Men's Lightweight Base Layer Tops

(28 products)
Products (28)
Sort: Best Match
  • Sale Ends May 25
    REI Co-opLightweight Long-Sleeve Crew Base Layer Top - Men's
    $33.69
    Save 25%
    compared to  $44.95
    41 reviews with an average rating of 4.4 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big, Tall
  • Sale Ends May 25
    Top Rated
    REI Co-opMerino 185 Long-Sleeve Half-Zip Base Layer Top - Men's
    $67.39
    Save 25%
    compared to  $89.95
    138 reviews with an average rating of 4.5 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    Top Rated
    SmartwoolClassic All-Season Merino Long-Sleeve Base Layer Top - Men's
    $74.99
    Save 25%
    compared to  $100.00
    106 reviews with an average rating of 4.6 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    Top Rated
    REI Co-opMerino 185 Long-Sleeve Base Layer Top - Men's
    $59.89
    Save 25%
    compared to  $79.95
    228 reviews with an average rating of 4.6 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    REI Co-opLightweight Half-Zip Base Layer Top - Men's
    $37.39
    Save 25%
    compared to  $49.95
    24 reviews with an average rating of 4.4 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
  • Text reads: ‘Anniversary Sale 2026. 25% off’ over a collage of Smartwool long-sleeve shirts and colorful socks.

    Save 25% on all Smartwool clothing

  • Sale Ends May 25
    Top Rated
    REI Co-opLightweight Crew Base Layer Top - Men's
    $26.19
    Save 25%
    compared to  $34.95
    32 reviews with an average rating of 4.6 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big, Tall
  • Sale Ends May 25
    SmartwoolClassic All-Season Merino T-Shirt - Men's
    $71.19
    Save 25%
    compared to  $95.00
    112 reviews with an average rating of 4.0 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
    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
    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
  • Sale Ends May 25
    REI Co-opMerino 185 Base Layer Top - Men's
    $52.39
    Save 25%
    compared to  $69.95
    60 reviews with an average rating of 4.3 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular
    Top Rated
    Arc'teryxRho LT Zip-Neck Base Layer Top - Men's
    $120.00
    111 reviews with an average rating of 4.5 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    Top Rated
    REI Co-opMerino 185 Long-Sleeve Half-Zip Base Layer Top - Men's Tall Sizes
    $67.39
    Save 25%
    compared to  $89.95
    17 reviews with an average rating of 4.8 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Tall, Big
    Top Rated
    Arc'teryxRho LT Crew Neck Base Layer Top - Men's
    $100.00
    45 reviews with an average rating of 4.8 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    SmartwoolIntraknit Thermal Merino Colorblock Crew Base Layer Top - Men's
    $97.49
    Save 25%
    compared to  $130.00
    13 reviews with an average rating of 4.2 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
    KUHLReactiv Lite Grid Long-Sleeve Crew Base Layer Top - Men's
    $109.00
    11 reviews with an average rating of 4.5 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
  • Sale Ends May 25
    Top Rated
    REI Co-opMerino 185 Long-Sleeve Base Layer Top - Men's Tall Sizes
    $59.89
    Save 25%
    compared to  $79.95
    11 reviews with an average rating of 4.8 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Tall
    Top Rated
    Arc'teryxRho LT Base Layer Hoody - Men's
    $120.00
    97 reviews with an average rating of 4.9 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
    KUHLReactiv Lite Grid Quarter-Zip Base Layer Top - Men's
    $119.00
    12 reviews with an average rating of 4.3 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
    Helly HansenLIFA Stripe Crew Base Layer Top - Men's
    $50.00
    0 reviews
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
    Top Rated
    Free CountryForce Grid Fleece Base Layer Top - Men's
    $22.73
    Save 49%
    compared to  $45.00
    18 reviews with an average rating of 4.9 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Big
    REI OUTLET
    Free CountryCloud Knit Crewneck Base Layer Top - Men's
    $26.73
    Save 33%
    compared to  $40.00
    10 reviews with an average rating of 4.0 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Big, Regular
    REI OUTLET
    Ortovox185 Rock'N'Wool Long-Sleeve Base Layer Top - Men's
    $120.00 - $130.00
    0 reviews
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
    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
    Top Rated
    IcebreakerMerino 125 ZoneKnit Long-Sleeve Half-Zip Base Layer Top - Men's
    $88.73
    Save 34%
    compared to  $135.00
    16 reviews with an average rating of 4.8 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular
    REI OUTLET
    Ortovox120 Comp Light Base Layer Hoody - Men's
    $120.00
    2 reviews with an average rating of 5.0 out of 5 stars
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
    Ortovox185 Rock'N'Wool Zip Neck Base Layer Top - Men's
    $130.00
    0 reviews
    Underwear Weight:
    Lightweight
    Size Type:
    Regular, Big
  • Limited time only! The R E I Co-op Mastercard.

    Get $130 in value

    When approved for the REI Co-op Mastercard by May 25, you’ll get $30 in card rewards. Plus, you can earn a $100 REI gift card after your first non-REI purchase within 60 days from account opening. Terms apply.

    Icebreaker125 ZoneKnit Crewe Base Layer Shirt - Men's
    $84.73
    Save 26%
    compared to  $115.00
    7 reviews with an average rating of 4.4 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:
    Big, Regular
Sort: Best Match