Love these and they wash so well
"Icebreaker make fabulous underwear will never go back to cotton. Love the colour, hoping to get a bra to match"
Free shipping and returns
$40.00
This item's price has been updated recently to ensure you get the best value.
Last priced at -
Enter your email to receive a notification when this product becomes available.
$40.00
This item's price has been updated recently to ensure you get the best value.
Last priced at -
Soft and stretchy merino wool underwear with a modern slim fit, the Siren Bikini features our corespun fabric that’s incredibly soft and durable.
Good for:

83% Merino Wool/ 12% Nylon/ 5% Elastane, Exclusive of decoration
Machine wash cold gentle cycle. Wash with like colors. Do not use softeners. Do not bleach. Do not tumble dry. Line dry in shade. Cool iron. Do not iron print. Do not iron decoration. Do not dry clean.
Fit
Slim
Overall rating: 4.6365104 / 5 from 619 reviews.
The Women's Merino 150 Siren Bikini is praised for its soft, breathable, and durable fabric. Customers appreciate its good quality and stylish appearance. However, opinions on sizing and coverage vary among users.
Review topics: ["fit","size","weight","problem","quality","delivery","feel","value","design","looks","fabric","price","material","style","comfort","colour","shape","wear","weather","packs","moisture","medium","comfy","works","waist","cotton","summer","underwear","pattern","durability"].
"Icebreaker make fabulous underwear will never go back to cotton. Love the colour, hoping to get a bra to match"
— Zozo (5/5)
"Love the shape, the quality is fantastic. The green is such a lovely green. Really muted and soft"
— Zozz (5/5)
"I procrastinated “splurging”on these for the longest time and they really are worth it. Great for traveling and working out, and they’re sustainably made."
— Al (5/5)
"These are awful. I have probably a dozen pairs of Icebreaker bikini & hipkini briefs. I love their breathability, but have always been frustrated by how quickly they develop holes. This is the worst pair I've had by far (passion color, 150 merino). They developed a number of holes on the first wash."
— Lina H. (1/5)
"The wool is nice but I still get weggies. I try to use these on high activity days where I’m going to sweat a lot- gym skiiing etc…They are breathable I just prefer a different style."
— Anonymous (4/5)
"I'm a M/L for underwear and bought a large but they don't cover my crack when I'm sitting. Alternated between 2 pairs for a 3 week rafting trip and loved the material but wish fit my butt got quite annoying when rowing."
— Anonymous (3/5)
"This is my favourite underwear. I love that the two pack offers them at a bit of a lower price."
— Ashley (5/5)
"Very nice soft fabric. Doesn’t lose elasticity like some other merino wool undies I’ve tried. Comfortable and helped wick moisture during workouts!"
— Anonymous (5/5)
"Once I went marino and specifically Icebreakers I could never go back. There's no comparison to thick swampy cotton underwear living in the south or sweat/stink holding synthetics (and messing with your lady biome) after long days running on the trail. Seriously these fit great for me (size: sm 5'3 120lbs athletic build-runner) stay in place and never smell. The only reason I give them 4 stars is because I have been buying these for a decade now and in recent years they do seem to wear thin faster."
— Anonymous (4/5)
"I purchased the Women’s Merino 150 Siren Bikini for my wife, and she absolutely loves them. The merino wool is incredibly soft and breathable—nothing like traditional wool that can feel itchy. They’re lightweight, comfortable, and perfect for everyday wear, whether at home, traveling, or layering for outdoor adventures. She especially appreciates how well they regulate temperature and wick moisture, keeping things fresh throughout the day. The fit is flattering and stays in place without digging in or bunching up. They also wash and wear really well, maintaining their shape and softness over time. Icebreaker has really mastered comfort and practicality with this design. Highly recommended for anyone looking for premium-quality, natural-fiber underwear that feels as good as it performs."
— Joshua N. (5/5)
Find the size that fits you best based on people just like you.

Use the chart below to determine your size. If you’re between two sizes, order the smaller size for a tighter fit or the larger size for a looser fit. If your measurements for chest and waist correspond to two different sizes, order the size indicated by your chest measurement for tops and your hip measurement for pants.
Sizing charts:
| XS | S | M | L | XL | XXL | |
|---|---|---|---|---|---|---|
| Waist | 24-26 | 26-28 | 28-30.5 | 30.5-33 | 33-36 | 36-40 |
| Hip | 33.5-35.5 | 35.5-38 | 38-40 | 40-42.5 | 42.5-45 | 45-48.5 |
| XS | S | M | L | XL | XXL | |
|---|---|---|---|---|---|---|
| Waist | 61-66 | 66-71 | 71-77 | 77-84 | 84-91 | 91-101 |
| Hip | 84-90 | 90-96 | 96-102 | 102-108 | 108-114 | 114-123 |
*Looking for the inseam length? Please refer to the product page to find out.
Our three different fits - slim, regular, and relaxed - ensure that when worn together, layers move and breathe like a single garment.



Your cart is empty

You’re now subscribed to our email list and will be the first to hear about new arrivals and special offers.
You are already set to receive the latest offers and news.

Welcome to the flock. Check your texts to confirm your subscription and receive your discount code. This offer is only valid for first-time subscribers.