Trade dress is the source-identifying look of a product or business—its packaging, shape, color, and overall image—protected under the Lanham Act even though the statute never uses the phrase. This UpLaw research article breaks the doctrine into the three things a claimant must prove: distinctiveness, non-functionality, and likelihood of confusion. It explains the bright-line rule of Wal-Mart Stores, Inc. v. Samara Bros. that product design can never be inherently distinctive, the functionality bar that kills more claims than anything else under Inwood, Qualitex, and TrafFix, and the Seabrook and Morton-Norwich frameworks the USPTO applies. It works through registration mechanics on the Principal Register, enforcement for infringement and dilution, the standard defenses, and remedies, all illustrated with invented hypotheticals and marquee disputes from the Coca-Cola bottle to the Louboutin red sole and the Supreme Court's 2023 Jack Daniel's decision. The piece closes with a working protection playbook and cross-references to related UpLaw resources.