Opinion of the Court
“in fact serve as a ‘trademark’ to identify and distinguish goods.” 3 McCarthy §19:10 (listing the principal register’s eligibility standards). If it does, and the statute’s other criteria also are met, the registering trademark owner receives certain benefits, useful in infringement litigation. See, e.g., Iancu v. Brunetti, 588 U. S. ___, ___ (2019) (slip op., at 2) (noting that “registration constitutes ‘prima facie evidence’ of the mark’s validity”). But the owner of even an unregistered trademark can “use [the mark] in commerce and enforce it against infringers.” Ibid.
The Lanham Act also creates a federal cause of action for trademark infringement. In the typical case, the owner of a mark sues someone using a mark that closely resembles its own. The court must decide whether the defendant’s use is “likely to cause confusion, or to cause mistake, or to deceive.” §§1114(1)(A), 1125(a)(1)(A). The “keystone” in that statutory standard is “likelihood of confusion.” See 4 McCarthy §23:1. And the single type of confusion most commonly in trademark law’s sights is confusion “about the source of a product or service.” Moseley v. V Secret Catalogue, Inc., 537 U. S. 418, 428 (2003); see 4 McCarthy §23:5. Confusion as to source is the bête noire of trademark law—the thing that stands directly opposed to the law’s twin goals of facilitating consumers’ choice and protecting producers’ good will.
Finally, the Lanham Act creates a cause of action for the dilution of famous marks, which can succeed without likelihood of confusion. See §1125(c); Moseley, 537 U. S., at 431. A famous mark is one “widely recognized” by the public as “designati[ng the] source” of the mark owner’s goods. §1125(c)(2)(A). Dilution of such a mark can occur “by tarnishment” (as well as by “blurring,” not relevant here). §1125(c)(1). As the statute describes the idea, an “association arising from the similarity between” two marks—one of them famous—may “harm[] the reputation of the famous mark,” and thus make the other mark’s owner liable.
