Where to sell a brand new/without alterarions wedding dress?

There are some stores that will buy your dress from you! Search for secondhand bridal shops in your area, and reach out to them. You can also try selling your dress on Facebook Marketplace, Facebook wedding resale groups for your state/area, eBay, Poshmark, Stillwhite, and Craigslist. You will most likely not get what you paid for it, though you can get at least some of your money back.

I’m having the same problem. Try sites like Still White, EBay, Poshmark, and Mercari!