Dirty laundry is a hotbed of odor and germs, so the more you can keep your clean and dirty clothes separate throughout your travels (as in, please don’t just throw them into the same suitcase compartment nilly-willy), the better.
Laundry bags like these by JHX are all you need: The bags fold down flat and to about the length of a cell phone when not in use, so you can easily chuck them in your luggage. They can hold up to 22 pounds of clothing and have helpful features like a drawstring slider, carrying handles, carabiners to clip onto another bag, an outer pocket for detergent or other items and a nylon material that is itself machine-washable, so you can truly throw everything into the machine as needed. You can buy a single or two-pack (pictured here) in gray or black.
Promising review: “These bags are great! The amount of clothes that fit in the bags is way more than I expected. I ordered these while on a two week vacation to take back new clothes I bought as well as dirty laundry. The handles on the bags are super helpful, all the other ones I looked at only had the drawstring. Highly recommend these!” —Jamie Munsey
Get it from Amazon for $7.19+.