Root beer is a sweet North American soft drink traditionally made using the root bark of the sassafras tree Sassafras albidum or the vine of Smilax ornata (known as sarsaparilla, also used to make a soft drink, sarsaparilla) as the primary flavor. Root beer is typically but not exclusively non-alcoholic, caffeine-free, sweet, and carbonated. Like cola, it usually has a thick and foamy head. A well-known use is to add vanilla ice cream to make a root beer float.

Since safrole, a key component of sassafras, was banned by the U.S. Food and Drug Administration in 1960 due to its carcinogenicity, most commercial root beers have been flavored using artificial sassafras flavoring, but a few (e.g. Hansen's) use a safrole-free sassafras extract.

Major root beer producers include PepsiCo, Coca-Cola Company, Dad's, Keurig Dr. Pepper, and A&W.