Merino Wool Base Layer: 17 Best Picks for UK Hikers 2025

Searching for a base layer that stays cosy on a frosty Munro yet breathes on a breezy ridge? The 17 merino pieces below are, weight for weight, the warmest and best-value tops and leggings you can buy in the UK for three-season and winter hiking through 2025. Merino’s natural thermoregulation, odour resistance and buttery feel make them clear winners over clammy synthetics.

Each pick earned its spot by ticking six boxes: UK stock, fabric weights from 150 g/m² to 260 g/m², men’s and women’s fits, fair price brackets, sound eco-credentials and proven trail performance. 100 % merino excels for softness and smell control, although blends toughen it up. The downsides are mostly cost and careful washing—both flagged item by item. Aim for a close fit that never feels corset-tight.

Quick primer: light merino (≤170 g/m²) suits sweaty summer ascents, mid-weight (180–230 g/m²) covers spring and autumn, heavy (>240 g/m²) sees off sleet and spindrift. Flat-lock seams, raglan shoulders and a drop tail prevent rucksack rub. Scroll straight to the picks or pause for the bite-sized buying tips and FAQs inside each box.

1. Icebreaker 200 Oasis Long Sleeve Crew

The Oasis is the yard-stick merino wool base layer for UK hikers—light enough for a sweaty scramble up Tryfan yet warm enough to sit out a Cairngorm white-out once you add a shell.

Quick Specs

• 200 g/m², 100 % merino
• Approx. 228 g in a men’s M
• Crew neck; men’s XS–XXL, women’s XS–XL
• RRP £85; widely stocked (Cotswold Outdoor, Ellis Brigham, Icebreaker UK)

Why it’s great for UK hikes in 2025

• Year-round “Goldilocks” weight straddles three seasons, so one top covers most trips.
• Merino fibres naturally kill pong—wear it three days on the West Highland Way without frightening the bothy.
• Offset shoulder seams and a drop tail sit smoothly under pack straps and waist-belts.

Things to watch

• Fine knit can snag on Velcro or gorse; pack a bit of Tenacious Tape.
• Pure wool needs a 30 °C wool cycle and mild detergent to maximise lifespan.

Value & Buying Tips

• Icebreaker’s January sale frequently hits 30 % off—ideal time to upgrade.
• If you sleep cold, the similar RealFleece 260 offers extra loft for roughly a tenner more.

2. Smartwool Merino 250 1/4 Zip

Smartwool’s beefy 250 g/m² quarter-zip is the one you pull on when the forecast reads single digits and sleet. A touch heavier than the Icebreaker Oasis, it locks in extra heat yet lets you dump steam quickly by yanking the zip at rest stops.

Quick Specs

• Fabric weight: 250 g/m², 100 % ZQ-certified merino
• Half-zip mock neck for on-the-move venting
• Men’s S–XXXL, women’s XS–XXXL (rare inclusive range)
• Average weight 285 g (men’s L)
• RRP £100; stocked at Smartwool UK Outlet, Trekitt, Snow+Rock

Why it’s great for UK hikes in 2025

• Built for cold, wet British winters: excels under a shell on a stormy Pennine Way leg.
• Body-mapped shoulder panels reduce seam bulk beneath rucksack straps.
• Naturally odour-resistant wool lets you stretch mileage between bothy wash-ups.

Things to watch

• Warmth comes with weight; stash a lighter tee for pub stops or unseasonably mild spells.
• Pure merino fibres can shrink if you crank the tumble-dryer—air-dry flat.

Value & Buying Tips

• Smartwool’s spring outlet drops often hit 40 – 50 % off—set a price alert.
• Lifetime guarantee covers seam or fabric failures, making the higher upfront cost easier to swallow.

3. Rab Syncrino Light Long-Sleeve Tee

Rab’s lightest merino blend tees weigh next to nothing yet out-perform many heavier tops when the pace ramps up.

Quick Specs

• 53 % merino / 47 % recycled polyester with TENCEL™
• Ultralight 145 g/m² fabric; men’s & women’s XS–XXL
• Crew neck, raglan sleeves; 115 g in men’s M
• RRP £65; stocked at Rab UK, Snow+Rock, Webtogs

Why it’s great for UK hikes in 2025

• Blend wicks sweat and dries markedly faster than pure wool—ideal on muggy Lake District fells or July scrambles on Skye.
• Sub-150 g weight stuffs into a fist, so you can carry a spare without noticing.
• Soft TENCEL™ fibres bump next-to-skin comfort; flat-lock seams keep shoulder rub at bay under a 40 L pack.

Things to watch

• Slight synthetic hand-feel may disappoint merino purists.
• Close athletic cut—size up if you prefer a looser camp fit (base layers should hug, not strangle).

Value & Buying Tips

• Rab’s “Seconds as New” outlet lists near-perfect returns at 25 % off—grab neutral colours early.
• Register for Rab’s newsletter; a 10 % welcome code frequently applies to full-price Syncrino pieces.

4. Finisterre Harlyn 185 Merino Crew

4. Finisterre Harlyn 185 Merino Crew

Quick Specs

• 185 g/m² Australian merino (non-mulesed)
• Plastic-free paper packaging
• Men’s S–XXL, women’s 8–18
• Average weight 190 g (men’s M)
• RRP £70; sold via Finisterre stores, website and John Lewis

Why it’s great for UK hikes in 2025

Cornwall-based Finisterre designs for damp Atlantic squalls, so this mid-weight knit keeps warming even when Cornish mizzle soaks through your shell. The understated crew styling means one tee works for dawn summits and post-trail pints, trimming pack weight for hut trips. Fine 18.5 µm fibres feel silky next to skin and the set-in sleeves slide neatly under a soft-shell.

Things to watch

• Tailored “surf fit” runs slim—size up if broad-shouldered.
• Light colourways show rucksack strap grime quickly.

Value & Buying Tips

Trade in any battered knit via Finisterre’s “Lived & Loved” scheme and pocket a 15 % voucher towards a fresh Harlyn. Sign up to their newsletter—seasonal drops often include a loyalty code worth another fiver.

5. Montane Primino 140 Zip Neck

Primino blends merino’s odour-busting fibres with PrimaLoft® polyester yarn to build a tee that behaves like wool yet dries like a synthetic—gold dust when the British forecast swings from drizzle to bright sunshine in a single hour.

Quick Specs

• 50 % merino, 25 % PrimaLoft® polyester, 25 % PrimaLoft® yarn
• Ultralight 140 g/m² fabric; deep front zip for venting
• Men’s S–XXL, women’s 8–18; average weight 130 g (men’s M)
• UPF40 sun protection; flat-lock seams, raglan sleeves
• RRP £75; available via Montane UK and major outdoor retailers

Why it’s great for UK hikes in 2025

On sweat-soaked grinds up Brown Willy or steady jogs along the South Downs Way, the hybrid knit moves moisture 30 % faster than pure merino, yet still keeps a chill off when you pause on a windy trig. The deep zip dumps heat instantly, while fine fibres (18.5 µm) stay itch-free against salt-stung skin. Built-in UPF40 saves slapping on extra sunscreen during cloud-breaks.

Things to watch

• Subtle sheen divides opinion on camp-fire aesthetics.
• Ultra-light fabric can ladder if caught on thorn; pack a needle kit.

Value & Buying Tips

Montane’s “Seasonal Specials” page regularly drops last year’s colours to £55. Student beans users snag an extra 10 % off, nudging this high-tech layer firmly into bargain territory.

6. Alpkit Kepler 200 Merino Leggings

Alpkit’s Kepler leggings channel Cumbrian practicality into a no-frills lower layer that keeps your legs toasty without smashing the budget.

Quick Specs

• 200 g/m², 100 % merino
• Wide comfort waistband, gusseted crotch
• Men’s S–XXL, women’s 8–16
• RRP £60; direct from Alpkit

Why it’s great for UK hikes in 2025

Close-fitting knit seals warmth for sub-zero starts on the Glyders yet stretches easily when high-stepping boulders. Merino kills odour, so one pair sees you through a two-day wild camp. The gusset and 40 mm waistband prevent chafe under a loaded hip-belt.

Things to watch

• No fly in men’s cut
• Wool knees can fuzz under rough crampon straps

Value & Buying Tips

Alpkit repairs free for three years and often bundles a 10 % discount when you add any Kepler top.

7. Aclima WarmWool Hooded Sweater

7. Aclima WarmWool Hooded Sweater

Quick Specs

• 200 g/m² 100 % merino
• Built-in balaclava hood, thumb loops, long drop-tail
• Unisex XXS–XXL (Norwegian sizing – runs small)
• RRP £110; stocked at Nordic Outdoor, Trekinn

Why it’s great for UK hikes in 2025

Pull the hood up and you’ve instantly got a beanie, buff and face mask—handy when spindrift whips across the Cairngorm plateau yet you don’t want loose accessories. The medium knit breathes on the climb but traps air once a hard shell goes on, making it a true four-season all-rounder. Flat seams and raglan shoulders play nicely with 60 L winter packs.

Things to watch

• Close-fitting hood can feel restrictive; try before you buy.
• Norwegian cut is long and slim—size up if broad-shouldered.

Value & Buying Tips

Nordic Outdoor’s January clearance usually drops WarmWool to under £80, and Aclima offers replacement hoods for repair instead of landfill.

8. Decathlon Forclaz Travel 190 Merino LS

Quick Specs

• 190 g/m² fabric, 89 % merino (19 µm), 11 % polyamide core-spun
• Crew neck; men’s S–XXXL, women’s XS–XL
• Avg. weight ≈ 210 g (men’s L)
• RRP £39.99 at UK Decathlon stores & online

Why it’s great for UK hikes in 2025

Dipping a toe into the merino wool base layer world? This is the cheapest genuine option that still holds its own on a damp Kinder Scout traverse. The nylon-wrapped core yarn beefs up abrasion resistance, so shoulder straps and hip-belts don’t saw through the fabric after one season. A true 190 g/m² mid-weight balances warmth and breathability, making it a one-top solution for spring and autumn overnighters.

Things to watch

• Colour choices lean “city travel” more than “mountain neon”.
• Straight torso can creep above the waist on long-torso hikers—size up if in doubt.

Value & Buying Tips

Grab the Decathlon app; new users usually get a £5 voucher, dropping your outlay to ~£35. At that price, buying two and rotating on multi-day treks still undercuts many single-layer rivals.

9. Mountain Warehouse Merino Long Sleeve Top

Quick Specs

• 80 % merino / 20 % polyester
• 200 g/m² knit, crew neck
• Men’s S–XXXL, women’s 8–20
• RRP £45; 常 “buy one get one half price” promos

Why it’s great for UK hikes in 2025

Need a last-minute layer before a wet weekend in Snowdonia? You’ll find this top on almost every UK high street. The 200 g/m² fabric holds warmth during steady family walks yet vents enough for brisk climbs, while the polyester threads harden the wool against repeated machine washes—handy if it doubles as school-trip kit.

Things to watch

Synthetic blend means funk sets in faster than 100 % merino, so expect a wash after two solid days. Set-in shoulder seams can chafe under big winter packs; smear anti-chafe balm if you’re carrying 60 L loads.

Value & Buying Tips

Stack the perpetual BOGOF offer: two tops cost ~£34 each. When buying in store, run a quick eye over the stitching—rare missed loops are easiest to swap on the spot.

10. EDZ 200g Merino Crew (Made in UK)

Quick Specs

• 200 g/m² 100 % merino knit
• Cut and sewn in Cumbria, England
• Men’s S–XXXXL, women’s 8–24 (rare plus-size span)
• Drop-tail hem, flat-lock seams
• RRP £55; available direct from EDZ and select Lake District shops

Why it’s great for UK hikes in 2025

Buying local trims carbon miles and supports a small British factory, yet you still get benchmark merino performance: soft next-to-skin feel, reliable odour control and enough warmth for breezy ridge walks from April through December. The generous size range means almost every hiker can achieve the close, movement-friendly fit a base layer needs to work properly.

Things to watch

Aesthetics are pure function—no jazzy colours or chest logos—so it won’t win pub-style points. Fine wool pills slightly after repeated rucksack abrasion (cosmetic only).

Value & Buying Tips

EDZ gives a 14-day no-quibble return and often bundles free UK postage; grab two and rotate on multi-day treks without blowing the budget.

11. Helly Hansen Lifa Merino Midweight Crew

11. Helly Hansen Lifa Merino Midweight Crew

Quick Specs

• Two-layer knit: Lifa® polypropylene inner + 225 g/m² merino outer
• Crew neck; men’s S–XXXL, women’s XS–XXL
• Flat-lock, shoulder-free seams
• RRP £70; widely stocked across UK retailers

Why it’s great for UK hikes in 2025

The hydrophobic Lifa® yarn sits next to skin, hauling sweat outward while the merino face fabric keeps insulating even when damp. That combo stops the dreaded “evaporation chill” during stop-start winter fell runs or icy scrambles. The slick inner also glides under mid-layers, so nothing bunches beneath a harness or sternum strap.

Things to watch

Polypro fibres pick up odour faster than pure wool—plan a rinse after two hard days. Trim, athletic cut; size up if you like a bit of wiggle room.

Value & Buying Tips

A standing 10 % student discount stacks with outlet colours that frequently drop to £49, making this one of the best-value hybrid base layers around.

12. Odlo Natural+ Kinship Warm Base Layer

Odlo took the popularity of its Kinship “snowflake” pattern and backed it with serious fabric engineering. The result is a winter-ready merino blend that feels plush, looks sharp and regulates heat so well you can leave the heavy fleece at home.

Quick Specs

• 52 % merino / 30 % polyester / 13 % polyamide / 5 % elastane
• Zoned, seamless knit––approx. 240 g/m² overall
• Men’s S–XXL, women’s XS–XL
• Stylish graphic print; crew or half-zip options
• RRP £90

Why it’s great for UK hikes in 2025

Body-mapped panels put thicker wool across the core while open-knit mesh under arms and along the spine turbo-charges moisture escape on lung-busting Glen Coe zig-zags. The stretchy, near-seamless torso eliminates hotspots under a stuffed 65 L pack and the Scandi pattern means it doubles as chalet lounge wear.

Things to watch

• Print can fade or shrink if tumble-dried; stick to 30 °C wool cycle and line dry.
• Athletic cut: size up for a relaxed bivvy fit.

Value & Buying Tips

Odlo’s newsletter regularly drops Black Friday codes worth 50 %—last November the Kinship fell to £45. Sign up early and pounce when your size re-stocks.

13. Patagonia Capilene Air Crew

Patagonia’s Capilene Air Crew blends lofty merino with recycled polyester in a 3-D knit that’s freakishly light yet traps serious heat on frosty ridgelines.

Quick Specs

• 51 % merino / 49 % recycled polyester blend
• Lofted 3-D knit; approx. 190 g garment weight
• Unisex slim fit, XXS–XXL
• RRP £130, Fair Trade Certified™ sewn
• Packs to grapefruit size; dries fast

Why it’s great for UK hikes in 2025

• Insulates like a 250 g/m² layer but weighs half as much.
• Open-cell weave dumps sweat instantly on lung-busting climbs.
• Soft, seam-free torso prevents pack-strap hot spots.

Things to watch

• Loose weave snags on Velcro and heather; handle gently.
• Pricey for a blend; pure-wool rivals cost less.

Value & Buying Tips

• Check Patagonia Worn Wear—gently used tops hover around £80.
• Sign up for the winter sale; last year new stock dipped to £99.

14. Woolpower Lite Zip Turtleneck

Quick Specs

• 80 % merino, 20 % polyamide rib knit (roughly 200 g/m²)
• Half-zip turtleneck; men’s S–XXL, women’s XS–XL
• Sewn in Östersund, Sweden – every seamstress signs the care label
• RRP £105; sold by Nordic Outdoor, BushcraftUK store

Why it’s great for UK hikes in 2025

The tall, close-fitting collar zips right under the nose, blocking spindrift on a Cairngorm plateau or chilly dawn start on the Pennine Way. The fine 1 × 1 rib stretches with dynamic moves yet springs back, so it layers cleanly beneath a soft-shell. Swedish build quality and hand-signed labels give genuine “buy once, cry once” confidence.

Things to watch

• Rib knit can pill where pack straps rub—purely cosmetic.
• Unisex cut is long in the torso; petite hikers may need to tuck excess length.

Value & Buying Tips

Woolpower almost never goes on deep sale; grab the bundled top + leggings set to save about 10 % versus individual prices.

15. Icebreaker 260 Tech Leggings

Quick Specs

• Heavyweight 260 g/m², 100 % merino
• Icebreaker BodyfitZONE™ knee panels add durability and stretch
• Wide elastic waistband; flat-lock seams
• Men’s S–XXL, women’s XS–XL
• RRP £90; easy to find at Cotswold Outdoor, Ellis Brigham and Icebreaker UK

Why they’re great for UK hikes in 2025

Sliding into these leggings is like fitting central heating to your legs: the dense knit traps serious warmth for summit camps on Ben Nevis or January dawn starts on the Pennine Way. Zoned knee panels stop fabric bagging when you’re high-stepping over stile or scrambling icy gullies, while pure merino keeps multi-day funk at bay.

Things to watch

• Overkill once temperatures climb above 5 °C—pack lighter tights as backup.
• Pure wool can take a while to dry if you soak them river-crossing.

Value & Buying Tips

Most UK retailers knock 10 % off when you bundle with the Oasis or any Icebreaker top—worth exploiting during winter kit refreshes.

16. Smartwool Intraknit 200 Crew

16. Smartwool Intraknit 200 Crew

Quick Specs

• 53 % merino, 43 % recycled polyester, 4 % elastane
• Target fabric weight: 200 g/m² with body-mapped 3-D knit vents
• Men’s S–XXL, women’s XS–XL
• Average weight 215 g (men’s M)
• RRP £115; limited UK distribution (Trekitt, Ellis Brigham, Smartwool Outlet)

Why it’s great for UK hikes in 2025

Intraknit weaves thicker wool over the core and kidneys while sculpting open-mesh panels under arms, down the spine and in elbow creases. The result? Furnace-like warmth on a frosty ascent of Blencathra yet rapid sweat dump when the pace spikes. Near-seamless construction eliminates pack rub and the added elastane lets the top stretch, rebound and hug without twisting under shoulder straps.

Things to watch

• Athletic, compression-style fit; size up if you fancy a roomier camp vibe.
• Open mesh can snag on hook-and-loop pockets—don’t wash it with Velcro gloves.

Value & Buying Tips

UK retailers receive small colour runs each September; popular sizes vanish fast, so pounce early or set an outlet alert for spring discounts of up to 30 %.

17. Amazon Essentials 100 % Merino Base Layer

Quick Specs

• 170 g/m², 100 % merino
• Crew neck; men’s S–XXL, women’s XS–XL
• Avg. weight 185 g (men’s M)
• Usually under £35 with Amazon Prime UK

Why it’s great for UK hikes in 2025

If you’re cash-strapped but still want real merino performance, this is the ticket. The 170 g/m² knit breathes well on sweaty summer ridge walks yet takes the edge off a cool campsite breeze. Prime’s next-day delivery is perfect for those Thursday-night “shall we head to Snowdonia tomorrow?” texts, and the simple cut layers cleanly under any mid-layer.

Things to watch

• No shoulder reinforcement; heavy 60 L packs will wear fabric faster.
• Fit runs boxy—size down if you’re slim and want next-to-skin efficiency.

Value & Buying Tips

Set a “Lightning Deal” alert; prices occasionally drop below £25. Buy two, rotate daily, and you’ll still spend less than a single premium top.

Stay Warm, Keep Walking

Nail the base layer and half the battle against British weather is already won. Pick a fabric weight that matches the season—light (≤170 g/m²) for midsummer sweat-fests, mid (180–230 g/m²) for blustery shoulder months, and heavy (≥240 g/m²) when frost rims the bothy door. Make sure the fit is snug enough to trap a sliver of warm air yet never restricts a high step. Finally, balance cost with durability: pure merino offers best next-to-skin comfort, whereas blends stretch longevity and shave a few quid.

Whichever of the 17 options you shoulder into, you’ll enjoy drier, less-whiffy miles and fewer shivery lunch stops through 2025. Just remember the bigger layering picture—add wicking socks, a lofted mid-layer and a breathable shell to keep that merino working at its best.

Ready to round out your wardrobe? Browse the full winter kit range over at take a hike uk and keep the adventure rolling, whatever the forecast throws at you.