The best underwear for working out is a breathable, seamless or laser-cut pair with a moisture-friendly cotton or modal gusset that moves with you and won't chafe. For the gym, you want knickers that sit flat under leggings to avoid a visible panty line, wick sweat away from the skin and stay put through squats, sprints and stretches. Comfort and breathability beat everything else.
- What underwear to wear to the gym
- Why breathable fabric matters for your workout
- No VPL, no chafe: cut and seams
- Thong, brief or Brazilian for the gym?
- Should you skip underwear under leggings?
- Our picks for gym-ready knickers
- Caring for gym knickers and how many you need
- FAQs
What underwear to wear to the gym
Good gym underwear does three jobs at once: it breathes, it stays invisible under tight kit, and it doesn't rub. That points you towards a seamless or laser-cut pair in a soft, sweat-friendly fabric with a comfortable gusset. Whether you go for a thong, a brief or a Brazilian comes down to your workout and what you find comfortable, not a single rule.
Workout underwear is a breathable, low-friction layer that manages moisture and prevents chafing. It is not the place for a stiff, fully synthetic pair with thick seams that trap heat and dig in. The wrong knickers can leave you adjusting them mid-set or dealing with irritation afterwards, so the fabric and cut genuinely matter.
If you're building out a whole move-with-you collection, our inclusive activewear edit is a good place to start.
Why breathable fabric matters for your workout
Exercise means heat and sweat, and the gusset of your underwear is exactly where that moisture collects. A breathable, absorbent fabric there keeps you drier and more comfortable, while a non-breathable synthetic traps warmth and damp against the skin.
This isn't only about comfort, it's about health. According to the NHS, wearing cotton underwear and avoiding tight underwear can help prevent thrush, because warm, moist conditions are exactly what the fungus that causes it thrives in. According to Cleveland Clinic, cotton is the best everyday choice because it's breathable and wicks away the excess sweat and moisture that bacteria and yeast feed on, while nylon traps heat and moisture instead.
That's why our knickers pair soft outer fabrics with a breathable cotton or modal gusset, so you get the best of both. Modal is a brilliant active-day fabric, and we explain exactly why in our guide to modal fabric.
| Fabric | Breathability | Moisture handling | Best for the gym? |
|---|---|---|---|
| Cotton gusset | High | Absorbs and wicks sweat | Yes, ideal next to skin |
| Modal blend | High | Soft, breathable, quick to dry | Yes |
| So-soft mesh | Very high | Airy, dries fast | Yes, very cooling |
| Pure nylon, no cotton panel | Low | Traps heat and moisture | Not for regular wear |
No VPL, no chafe: cut and seams
Tight leggings show everything, so the seams on your underwear decide whether you get a visible panty line. Seamless and laser-cut knickers have bonded or raw edges that lie completely flat, so nothing prints through. Traditional stitched hems can create ridges under thin, stretchy fabric.
Chafing comes from seams and fabric rubbing against the skin during repetitive movement. The flatter the construction and the smoother the fabric, the less friction you feel over a long session. A snug-but-not-tight fit also helps, because underwear that shifts around rubs more. According to the OEKO-TEX STANDARD 100 certification, which all of our fabrics carry, every component is tested against more than 1,000 substances that could be harmful in close skin contact, so the layer rubbing against your most sensitive skin during a workout is genuinely skin-kind.
For a full breakdown of styles that vanish under leggings, see our guide on Brazilian vs brief vs thong.
Thong, brief or Brazilian for the gym?
There's no single winner here, it depends on coverage and feel. A thong removes the back panty line entirely, which is why many people reach for one under tight leggings. A Brazilian gives a little more coverage at the back while still staying low-profile. A brief offers the most coverage and a secure, stay-put feel for high-intensity training.
| Style | Coverage | VPL under leggings | Great for |
|---|---|---|---|
| Thong | Minimal | None at the back | Lifting, yoga, tight leggings |
| Brazilian | Medium | Very low with seamless cut | Cardio, classes, everyday gym |
| Brief | Full | Low with laser-cut edges | HIIT, running, secure feel |
Our so-soft mesh thong is a cooling, near-invisible option, while the signature lace brief and signature lace Brazilian give you more coverage without bulk.
Should you skip underwear under leggings?
Some people prefer to go without underwear under gym leggings, and high-quality leggings with a built-in gusset can work for that. But it comes with a trade-off. Without a breathable cotton or modal layer between you and synthetic leggings, sweat and heat sit directly against sensitive skin for the whole session, and you can't easily change that layer afterwards.
According to the NHS, a warm, moist environment encourages the fungus that causes thrush, so a breathable, sweat-wicking gusset is the safer everyday choice for most people. A lightweight seamless thong gives you that protective layer with almost no bulk and no panty line, which is usually the best of both. Whatever you choose, changing out of damp kit promptly after training is the simplest healthy habit.
Our picks for gym-ready knickers
For a cooling, invisible feel, reach for the so-soft mesh thong. For a soft, breathable everyday option with a touch more coverage, the everyday eco thong is a brilliant all-rounder. Prefer full coverage? The signature lace brief stays put through anything. All of them use breathable fabrics and a skin-kind gusset, so they handle a workout and the rest of your day.
Still deciding what feels best for you? Our guide to the comfiest knickers to wear helps you match cut to comfort.
Caring for gym knickers and how many you need
If you train a few times a week, it's worth having enough gym-specific knickers that you never have to reach for a damp or stretched-out pair. Most people find five to seven dedicated pairs covers a full week of workouts plus laundry days, so there's always a fresh, breathable pair ready to go. Putting on clean, dry underwear before each session is one of the simplest ways to stay comfortable.
Looking after them keeps the fabric breathable and the fit snug. Wash on a cool cycle, ideally in a mesh laundry bag to protect delicate mesh and bonded edges, and skip the fabric softener, which can coat the fibres and reduce how well they wick moisture. Air-drying rather than tumble-drying preserves the elastane so the waistband and legs keep their stay-put stretch.
Because your underwear sits against your most sensitive skin while you sweat, knowing your fabrics are tested for safety matters. According to OEKO-TEX, the STANDARD 100 label means a textile has passed independent testing for harmful substances, which is the reassurance you want from kit you sweat in regularly. Build a small rotation of well-cared-for, breathable pairs and your gym drawer quietly sorts itself out for good.
FAQs
What is the best underwear for working out?
The best underwear for working out is a breathable, seamless or laser-cut pair with a cotton or modal gusset. It should move sweat away from the skin, lie flat under leggings to avoid a visible panty line, and fit snugly so it doesn't shift and chafe during exercise. Thongs, Brazilians and briefs can all work depending on the coverage you like.
Should gym underwear be cotton?
The gusset ideally should be. The NHS and Cleveland Clinic both recommend breathable cotton because it absorbs and wicks the sweat that bacteria and yeast thrive on, while synthetic fabrics trap heat and moisture. A soft outer fabric with a breathable cotton or modal gusset gives you comfort, a clean line and a skin-kind layer next to the skin.
Do thongs stop visible panty lines at the gym?
Yes, a thong removes the back panty line entirely, which is why it's a popular choice under tight leggings. For even smoother results, choose a seamless or laser-cut thong with bonded edges that lie completely flat, so nothing prints through thin, stretchy workout fabric.
Is it bad to wear no underwear under gym leggings?
It's a personal choice, and leggings with a built-in gusset can work, but going without means sweat and heat sit directly against sensitive skin for your whole session. The NHS notes that warm, moist conditions encourage thrush, so a breathable cotton or modal layer is the safer everyday option for most people. A lightweight seamless thong gives that protection with no bulk.
How do I stop chafing from gym underwear?
Choose seamless or laser-cut knickers with flat, bonded edges and a smooth, soft fabric, since seams and rough fabric cause most friction. A snug fit that stays put rubs far less than loose underwear that shifts around. Changing out of damp kit soon after training also keeps your skin comfortable.
