IcebreakerSiren Thong - Women's

A call to comfort.

The benefits of merino wool are well known—it's moisture wicking, breathable, antimicrobial, and excellent at regulating temperature—but making a thong out of it? You bet. Icebreaker's Siren Thong takes all the benefits of your favorite merino shirt down south, so you'll stay comfortable and free of lines whether you're wheeling and dealing at the office, going for a run at lunchtime, or ditching work altogether to go crush some boulders or fresh snow. The Siren's bulk-free waist and leg openings are virtually impossible to detect under tights and slinky dresses, and the strategically placed side seams won't rub you the wrong way when you decide that going for a hike is actually a much better idea than sitting in meetings all afternoon.

  • Merino wool blend
  • Bulk-free waist and leg openings
  • Strategically placed side seams
  • Reviews
  • Q & A


    I ordered the XS because that’s what was left. I was skeptical that it might be too small; but they fit perfectly. I’m 5’3” 125 lbs. Love’em!


    • Familiarity: I've put it through the wringer
    • Fit: True to size
    • Size Bought: Small

    I didn't even know I needed Merino underwear until these - they're perfect for travel, backpacking, biking... everything. I'm not wool's biggest fan, but they're not itchy in the slightest and they dry incredibly quickly.

    Who needs Victoria's Secret?

    • Familiarity: I've put it through the wringer
    • Fit: True to size
    • Size Bought: Small

    But seriously. These are the most comfortable, practical idea for active ladies. The Merino fabric is incredibly comfortable and noticeably breathable, washes really well, and dries super quickly. I brought a few pair of these along on a four day trip in the desert and they were so much more comfortable than my everyday cotton thongs. The fit is great too - the are a flattering rise that doesn't come up too high.

    If you have any further questions about this product I am happy to help! You can call me directly at 801-619-7488, or email me at

    New favorite underwear for Running

    • Familiarity: I've put it through the wringer
    • Fit: True to size
    • Size Bought: S

    I have several pairs of Icebreaker underwear already. I love the thong as I can wear it to go running/yoga and not have to be constantly picking a wedgie and worried about lines showing.
    The anti-microbial feature and Merino wool add extra comfort. Great for running ,backpacking, yoga, and so much more!

    Go to undies for camping/climbing/yoga

    • Size Bought: Medium

    Pleasantly surprised by these! They stay in place all day, aren't constricting, and wick away moisture as needed.

    New Favorite Undies

    • Familiarity: I've put it through the wringer
    • Fit: True to size
    • Size Bought: S

    I have ordered several pairs of the Icebreaker Hot Sprite pant that I've loved, but I did get a little [anite line wiht some jeans, and wanted to try the thong style out for running and spandex wear over top. Not only is the fit perfect, they are equally as comfortable as the Hot Sprite that I have, and now NO underwear line! Perfect for running, or wearing hiking the grand canyon like I did!
    A must have for lightweight backpacking, they only weigh a couple grams!


    • Familiarity: I've put it through the wringer
    • Fit: Runs large
    • Size Bought: extra small

    I was leary when I bought them but they far exceed my expectations. I love how comfortable and breathable they are. They do run large so size down.

    What size are you? I don't know whether to get small or xsmall. I'm 5'2 and 115lbs.

    Just the best.

    • Familiarity: I've put it through the wringer
    • Fit: True to size
    • Size Bought: medium

    Icebreaker does a stand out job with their undies, and these are no different. Thongs are tricky. It's all about the fit. They can be tight and restrictive, or so loose you feel like Borat at the beach. These are just right. I'm a medium-sized lady, and the medium is perfect. It doesn't pinch too much and doesn't ride too high. They sit right where most of my pants do.

    As for the fabric, if your not familiar with merino, it's THE fabric for intimates, especially if you'll be camping or backpacking. You can wear them for days, and still feel fresh and comfortable. They are one of my most important pieces, when backpacking.

    Also, Icebreakers quality is All-Star, without a doubt.

    Wool Underwear? Actually the best!

      I don't know if anyone else shared my immediate skepticism about wool underwear. Wool sweaters yes, but underwear?

      Oh how wrong I was. If you know Icebreaker's merino wool you will know, but for you others let me describe the softness, pliability, wicking, and general wonderfulness of these underwear. It almost feels like I'm not wearing underwear. They are so awesome, I'm almost sad when I wear them because then it has to be at least another laundry load before I can wear them again.

      The sizing is true to size. The slightly thicker top band keeps them from rolling or going rogue during the day. They are just so soft and comfortable!

      Love them! And if you love yourself, treat yourself and make sure you have underwear that loves you too.