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.
At a glance
Best running underwear for women: the quick answer
For thigh chafing on a run, pick a leg of 6 to 9 inches in a fabric that suits your distance.
- Long runs and race day: Runderwear Women's Anti Chafing Short, an 8 inch leg in recycled polyamide with silicone leg grippers, £23, with a 90 day chafe-free guarantee.
- Our pick for parkrun, the gym and walking: Flissie women's bamboo boxer shorts (we make them), a 6 inch leg in soft bamboo viscose, in every size from UK 8 to 30. £20 a pair, or about £13 a pair in a 7 pack.
- Trail and multi-day: Smartwool Intraknit Hipster, a merino blend, £35.99.
- Seam chafing rather than thigh rub: Runderwear Women's Running Briefs, seamless, £18 a pair or £43.20 for 3.
- Sizes up to UK 34: Chaffree KnickerBoxers, COOLMAX with a 6 or 8 inch leg, from £22.99.
Updated 7 October 2026. Prices checked on each brand's own website on 4 and 7 October 2026.
Try Flissie women's bamboo boxer shorts
£20 a pair, or £13 a pair in a 7 pack, in UK 8 to 30 at one price. Free UK delivery on every order, a free size swap on your whole first order, and a 60 day guarantee: full refund, worn or not.
Why you can trust this guide
★★★★★ 4.7 out of 5 from 336 reviews of Flissie women's bamboo boxer shorts, and about 2,500 customers since 2021.
- Who wrote it: Phillippa and Matthew, the founders of Flissie. We have designed and sold women's boxer shorts from Derbyshire since 2021.
- Our bias, stated: we make Flissie women's bamboo boxer shorts, and we say where they are the wrong choice: for long runs, pick a synthetic. Every product here, ours included, has a Cons line.
- No paid placements: no brand paid to be included, and none of the links earn us money.
- How we compared: leg length, fabric, sizes, price and returns, from each brand's own website on 4 and 7 October 2026, or a US retailer for New Balance. No lab tests and no medical claims.
"The material is very lightweight and breathable, and the sizing/fit is perfect. Love the colours!" Amalie, United Kingdom, verified buyer, August 2026
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 merino |
| 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 |
On a phone, swipe the table sideways to see every column.
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. For a wider comparison beyond running, including merino and absorbent pants, see our guide to sweat wicking underwear.
The 12 at a glance
| Pick | Best for | Leg | Fabric | Price |
|---|---|---|---|---|
| Runderwear Women's Anti Chafing Short | Thigh rub on long runs and race day | 8 inch | 92% recycled polyamide, 8% recycled elastane | £23 |
| Runderwear Women's Running Briefs | Seam chafing | Brief | Recycled technical fabric | £18, or £43.20 for 3 |
| Under Armour Pure Stretch No Show Hipster | A first pair in technical fabric | Hipster | 76% polyamide, 24% elastane | £29 for 3 |
| New Balance Performance Seamless Hipster | A cheap synthetic, if you can find it | Hipster | 93% nylon, 7% spandex | $17.95 for 3 (US retailer) |
| Lululemon UnderEase Super-High-Rise Shortie | Under high-rise leggings | 5 inch | 91% modal, 9% elastane | £24 to £39 for 2 |
| Gymshark FeatherForm Short | No lines under gym leggings | 3 inch | 78% nylon, 21% elastane, 1% polyester | £22 |
| Smartwool Intraknit Hipster | Trail and multi-day | Hipster | 42% merino, 38% lyocell, 12% nylon, 8% elastane | £35.99 |
| Tracksmith Brighton Briefs | A premium merino brief | Brief | 66% wool, 32% nylon, 2% elastane | £50 |
| Branwyn Essential Boyshort | Merino with more coverage | Boyshort, length not stated | 81% merino, 14% nylon, 5% elastane | $42 |
| Flissie women's bamboo boxer shorts (ours, our pick for shorter runs) | Parkrun, gym, walking and all-day wear | 6 or 9 inch | 95% bamboo viscose, 5% elastane | £20, about £13 each in a 7 pack |
| Thigh Society The Cooling | The widest choice of leg lengths | 5 to 21 inch | 78% polyamide, 20% elastane, 2% cotton | $40 |
| Chaffree KnickerBoxers | Sweat and thigh rub, up to UK 34 | 6 or 8 inch | COOLMAX | From £22.99 |
On a phone, swipe the table sideways to see every column.
Prices and specifications from each brand's own website on 4 and 7 October 2026. New Balance does not sell women's underwear on its UK site, so its row is from a US retailer.
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. £18 a pair, or £43.20 for a 3 pack in Runderwear's multibuy offer when we checked, sizes S 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 in the US, but hard to find here: New Balance's UK site does not list women's underwear, so you are relying on Amazon or a US retailer.
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 to stay put rather than 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.
Our pick for shorter runs and everyday wear, because Flissie women's bamboo boxer shorts (we make them) have a 6 inch leg that covers the thighs, with a 60 day guarantee, full refund, worn or not.
"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 (reviewer earned a reward for a future purchase)
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. 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 from UK 6 to 34.
Specifications and prices checked on each brand's own website on 4 and 7 October 2026, and at a US retailer for New Balance. We have no commercial relationship with any of these brands.
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 long enough 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, such as Flissie women's bamboo boxer shorts (ours), works well, 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 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.
Not sure about the size?
Flissie women's bamboo boxer shorts run from S (UK 8 to 10) to 3XL (UK 28 to 30), all at the same price. If you are between sizes, size up, and if the size is wrong, we swap your whole first order free. Every order has free UK delivery and a 60 day guarantee: full refund, worn or not.
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 parkrun, the gym and walking, Flissie women's bamboo boxer shorts (we make them) have a 6 inch leg, in UK 8 to 30. 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 Flissie women's bamboo boxer shorts (we make them) 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 put a smooth layer between your thighs. For long distance and heavy sweat, a technical synthetic manages moisture better, because bamboo viscose absorbs moisture rather than repelling it. We make Flissie women's bamboo boxer shorts 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.
How long should anti-chafing running underwear be?
Long enough to reach where your thighs touch, which for most people means a leg of 6 inches or more; briefs, hipsters and thongs stop short of it. Runderwear's Anti Chafing Short has an 8 inch leg, Chaffree comes in 6 or 8 inches and Thigh Society from 5 to 21 inches. Flissie women's bamboo boxer shorts (we make them) have a 6 inch leg in all 8 colours, with a 9 inch in black and pine green if you prefer a longer leg.
Should running underwear be tight or loose?
Close-fitting but not tight. The fabric needs full contact with your skin to glide rather than gather, so a pair that is too small is not safer, and sizing down usually makes riding up worse. If you are between sizes, size up.
Do I need anti-chafe balm as well as anti-chafing underwear?
For shorter runs, a long leg is usually enough on its own, because it puts a layer of fabric between your thighs. For a half marathon and above, wear a technical synthetic and consider an anti-chafe balm on top, because at that distance moisture management stops being a comfort question.
Sources
- Women's Running: the best running underwear
- Runderwear women's anti chafing shorts
- Runderwear chafe-free guarantee and returns (checked 8 October 2026)
- Cleveland Clinic: chafing causes and prevention
- OEKO-TEX Standard 100
