Best Running Underwear for Women: Anti-Chafing Picks by Distance and Fabric
We make bamboo viscose boxer shorts, so we are one of the options below. We have not run laboratory tests and will not pretend we did. We have also been straight about where our own product is the wrong choice, which is at the far end of this list.
The mechanism, before the brands
Thigh chafing while running is friction plus moisture. Two levers, and most people only pull one.
Leg length handles the friction. A 6 to 9 inch leg puts a soft layer between your thighs so they glide instead of catching. That mechanism works whatever the fabric is made of, and it is the reason most running underwear fails at it: the category is dominated by briefs, hipsters and thongs, none of which reach the point where thighs touch.
Fabric handles the moisture, and this is where it gets specific. The right fabric depends entirely on how hard and how long you are running, which is why this article is organised by that rather than by rank.
Choose your fabric by sweat level, not by brand
| Fabric | Moves moisture | Best for | Watch out for |
|---|---|---|---|
| Technical synthetic (nylon, polyester, elastane) | Fastest. Pushes moisture across the surface and off | Long distance, hot weather, heavy sweaters, race day | Holds odour more than natural fibres |
| Merino wool | Absorbs moisture while resisting odour | Multi-day, trail, cold weather, anyone who sweats and cannot change immediately | More expensive, needs careful washing |
| Bamboo viscose | Absorbs moisture, soft and temperature-regulating | Parkrun, walking, gym, low to moderate intensity, everyday wear either side of a run | Absorbs rather than repels, so it is not the choice for a marathon in July |
| Cotton | Absorbs and holds | Not running | Once wet it stays wet, and wet fabric is what turns friction into raw skin |
Women's Running magazine makes the same point: underwear designed for running beats everyday underwear, because absorbent fabrics soak up sweat and create the conditions for chafing.
Our own product is bamboo viscose. That puts us in the third row, not the first. We would rather tell you where the line is than pretend the fabric does something it does not.
The 12, grouped by what you are actually doing
For long distance and race day: technical synthetics
1. Runderwear Women's Anti Chafing Short. The obvious first recommendation for runners, and a UK brand. Built specifically around a longer inseam for thigh protection, with silicone leg grippers at the hem to stop ride-up. If your problem is thigh rub on long runs, this is the purpose-built answer.
2. Runderwear Women's Running Briefs. 360-degree seamless construction in technical fabric. Around £26 for a 3-pack, sometimes £22, sizes XS to XXL. A brief rather than a long leg, so it solves seam chafing rather than thigh chafing.
3. Under Armour Pure Stretch. Widely available, synthetic, and usually the cheapest way into technical fabric.
4. New Balance Performance. Another accessible synthetic option, stocked in most running retailers.
5. Lululemon UnderEase. Premium, very light, popular with people who want it invisible under leggings.
6. Gymshark Seamless. Aimed squarely at the no-visible-lines problem under gym leggings.
For odour control, multi-day and trail: merino
7. Smartwool Intraknit. Merino, and the standard recommendation when odour matters more than drying speed.
8. Tracksmith Brighton Briefs. Merino, premium, running-specific brand.
9. Branwyn Essentials. Merino, built for performance rather than as an everyday range.
For parkrun, gym, walking and everyday: soft long-leg options
10. Flissie 6" and 9" bamboo viscose boxers. Ours. The long leg is the point: it covers the inner thigh past where chafing starts, and the leg band is tensioned so it does not roll into a rope at the top of your thigh, which is the failure that makes most long-leg underwear useless. Soft, breathable and temperature-regulating. UK 8 to 30, every size the same price.
"What a great pair of pants, so comfortable. This is my first time trying a longer leg. Planning on buying more." Anonymous, United Kingdom, verified review
Where it loses: bamboo viscose absorbs moisture rather than repelling it. For a half marathon in August, a technical synthetic will keep you drier. It also wants a cool wash, so see the care guide.
11. Thigh Society The Cooling. A cooling nylon-based knit in lengths from 5 to 21 inches, OEKO-TEX Standard 100 certified. Sheer and very light, and the longest legs available anywhere in this list.
12. Chaffree KnickerBoxers. 78% COOLMAX in 6 or 8 inch legs, with a wide cotton gusset. A UK brand built specifically around sweat and friction, and the sizing runs to dress size 36.
Specifications checked against brands' own product pages in July 2026. We have no commercial relationship with any of these brands. See the verification note at the end.
What running underwear actually needs to do
Four things, in order of how often they go wrong:
- Not ride up. The most common failure. A leg band that rolls creates a rope of fabric exactly where you are trying to stop friction. Silicone grippers, a properly tensioned band or a genuinely long leg all solve it
- Not hold sweat against you. Which is the fabric decision above
- Not have a seam where you have friction. Flatlock or seamless construction, and no side seam sitting on the inner thigh
- Fit without bunching. Too tight is not safer. Fabric needs full contact to glide rather than gather
What to wear by distance
- Up to 5k, or a walk: almost anything that does not ride up. This is where a soft long-leg boxer is genuinely comfortable, and you can wear it for the rest of the day
- 5k to 10k: technical synthetic or a long leg, depending on whether your problem is sweat or thigh rub
- Half marathon and above: technical synthetic, and consider anti-chafe balm on top. At this distance moisture management stops being a comfort question
- Trail and multi-day: merino, because you will not be changing as often as you would like
- Gym and strength sessions: whatever is comfortable seated and does not roll. Less sweat volume than a run, more time in fixed positions
Cotton, and why every running guide tells you to avoid it
Cotton absorbs moisture and holds it. A cotton gusset stays wet for the whole run, and wet fabric against moving skin is what turns friction into raw skin.
This is the one piece of running-underwear advice that is genuinely universal, and it is worth knowing that it applies partly to bamboo viscose too, since both are absorbent fibres. Bamboo viscose dries faster than cotton and feels cooler, but it is not a technical synthetic and we are not going to describe it as one.
Your questions answered
What is the best underwear for running to prevent chafing?
For thigh chafing, a long leg of 6 inches or more, because that is what stops skin touching skin. Runderwear's Anti Chafing Short is the purpose-built running option. For seam and crotch chafing, a seamless technical brief. For most people the answer is a longer leg in a fabric that moves moisture.
What is the best running underwear for women?
Depends on distance. Technical synthetics such as Runderwear or Under Armour for anything over 10k, merino such as Smartwool for trail and multi-day, and a soft long-leg option such as ours for parkrun, gym and walking. Fabric matters more the further you go.
Is bamboo underwear good for running?
For shorter distances, walking and gym sessions, yes, and the long-leg versions solve thigh chafing well. For long distance and heavy sweat, a technical synthetic manages moisture better, because bamboo viscose absorbs moisture rather than repelling it. We make bamboo viscose boxers and we would still tell you that.
How do I stop my underwear riding up when I run?
Look for silicone leg grippers, a properly tensioned leg band, or a leg long enough that it has nowhere to roll to. Sizing down does not help and usually makes it worse, because the fabric needs full contact to stay put rather than gather.
Should I wear underwear under running leggings?
Personal preference. Many running leggings and shorts have a built-in liner designed to be worn without. If you prefer underwear, choose something seamless or long-legged so you are not adding a seam where you already have friction.
Are thongs good for running?
Some runners prefer them because there is no leg band to ride up and no visible line. They do nothing for thigh chafing, since there is no fabric between your thighs. It depends entirely on which problem you have.
What about men's running underwear?
We only make women's, so we are the wrong people to ask. Runderwear, Saxx and Under Armour all have well-regarded men's ranges. We mention it only because people land here looking.
How should I wash running underwear?
Skip fabric softener across all of these, because it coats fibres and reduces moisture-wicking. Technical synthetics and merino have their own requirements, so follow the label. Bamboo viscose wants a cool wash and air drying, covered in our care guide.
Sources
- Women's Running: the best running underwear
- Runderwear women's anti chafing shorts
- Cleveland Clinic: chafing causes and prevention
- OEKO-TEX Standard 100
