There’s nothing basic about base layers. The base layer (outdoor industry speak for “undergarment”) is the foundation for your entire outdoor clothing system, and it all starts next to the skin. From the choice in fabrics to the location of the seams, a lot of engineering goes into an outdoor base layer that sets it apart from a common cotton undershirt. It has to be comfortable, non-chafing, and wick away sweat to the outer clothing layers so you won’t stay damp. Being wet could be merely annoying, with the discomfort of shivering and chafing, or downright deadly if you’re in cold-weather conditions.

Two things we look for in a base layer are how lightweight it is and whether it has a hood. The latter isn’t necessary, but it’s supremely convenient on sunny days. There are a lot of undershirts and base layers out there; few are terrible, but few really stand out, either. These are our favorites.

Updated December 2021: We’ve added the Ibex Indie Hoodie and Uniqlo Heattech Crew Neck Long Sleeve T-Shirt, and we’ve added new retailers to existing products.

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