Best Men's Base Layers and Thermal Underwear for 2024

Our top pick, the Smartwool Classic Thermal Merino 1/4 Zip, effortlessly balances warmth, breathability, and comfort. Crafted from 100% merino wool, this midweight base layer excels at heat retention while still being breathable enough for various cold-weather activities. One of its standout features is the natural odor-resistance of merino wool, which keeps you feeling fresh even after long wear. The seamless construction ensures itch-free comfort, reducing chafing, and the quarter-zip design allows for easy temperature regulation. Whether you're layering up for skiing or wearing it on a chilly day out, this piece is versatile and reliable.

The Ibex Woolies Tech Long Sleeve Crew is our runner-up, known for its superior blend of durability, comfort, and moisture-wicking properties. This midweight merino wool base layer is perfect for both high-intensity and casual activities. It offers excellent odor resistance and breathability, ensuring you stay dry and comfortable all day long. The snug, form-fitting design not only retains heat but also layers easily under other clothing. While its price may be a bit steep, the performance and quality make it a worthy investment.

If you're on a budget but don't want to compromise on quality, the REI Co-op Lightweight Base Layer Crew is an excellent choice. Made from a blend of polyester and spandex, this lightweight base layer delivers on comfort and functionality. Its moisture-wicking capabilities and quick-drying nature make it suitable for various activities. Although it doesn't offer the same warmth as merino wool options, it's perfectly adequate for everyday use or light physical activities. The affordability combined with its performance makes it a solid pick for budget-conscious shoppers.

For those who engage in high-output activities like skiing or intense hiking, the Smartwool Intraknit Thermal Merino Crew is tailored for performance. This midweight base layer features a blend of merino wool and synthetic fibers, enhancing durability and moisture management. The seamless knitting technology targets insulation and breathability exactly where you need it, ensuring ultimate comfort during demanding activities. Its snug fit and technical design not only look great but ensure you stay warm and dry, making it an ideal choice for active users.

When facing extremely cold conditions, the Arc'teryx Rho Heavyweight Zip Neck stands out as the best heavyweight base layer. This base layer is made from a mix of polyester, nylon, and elastane, offering exceptional warmth and effective moisture-wicking properties. The close, cozy fit maximizes heat retention, while the zip neck lets you adjust for ventilation as needed. Although priced higher than most, its performance in frigid temperatures is unmatched, justifying the investment for those who need top-tier protection against the cold.