In United States patent law, patent misuse is a patent holder's use of a patent to restrain trade beyond enforcing the exclusive rights that a lawfully obtained patent provides. If a court finds that a patent holder committed patent misuse, the court may rule that the patent holder has lost the right to enforce the patent. Patent misuse that restrains economic competition substantially can also violate United States antitrust law.

Patent misuse is a patent owner's improper use of patent rights, speaking very generally, to expand the scope or term of the patent. Examples of such patent misuse include forcing customers to agree to pay royalties on unpatented products or to pay royalties on an expired patent. This particular type of patent misuse can take place without a violation of antitrust laws. But it violates such policies of US patent law as the monopoly of a patent is confined to what its claims cover and once a patent expires the public has an unlimited right to practice the formerly claimed subject matter.

Patent misuse may also occur when the patentee's conduct is a violation of antitrust laws. For example, a company buying all the patents in a given field (relevant market) to stall competition would be misusing patents, and (assuming other statutory requirements are met) also violating section 7 of the Clayton Act (15 U.S.C. § 18) and section 2 of the Sherman Act (15 U.S.C. § 2). Other antitrust patent misuse includes (again assuming that other statutory requirements are met) a licensor's exercising control over the price that several licensees charge for a product or service; attempting to enforce a patent that the patentee knows to be invalid or not infringed; and selling patented goods on the condition, agreement, or understanding that the buyer will not deal in the goods of a competitor of the seller.

In the early 20th century, patent misuse was not yet a well recognized defense to patent infringement, although it had been recognized in Adams v. Burke in 1873. Courts at that time recognized relatively few limitations to patentees' rights. In 1912, the Supreme Court did not recognize a doctrine of patent misuse in Henry v. A.B. Dick Co., a case in which a patent license was tied to a purchase of another product. According to the Court, because a patent owner had the greater right to withhold its patented product from market entirely, it had the inherent lesser right to selectively withhold it from people who did not purchase other products.

This inherent-right doctrine was expressly rejected a few years later, however, in Motion Picture Patents Co. v. Universal Film Mfg. Co. In that case, Justice Holmes (who had been in the majority in the A.B. Dick case), now in dissent, argued that because the owner of a patented teapot "may keep his device wholly out of use . . . I cannot understand why he may not keep it out of use unless the licensee, or, for the matter of that, the buyer" will agree to buy his tea from the patent owner. But the majority rejected this doctrine of patentees' "inherent rights." It explained:

[T]he argument [is] that, since the patentee may withhold his patent altogether from public use, he must logically and necessarily be permitted to impose any conditions which he chooses upon any use which he may allow of it. The defect in this thinking springs from the substituting of inference and argument for the language of the statute, and from failure to distinguish between the rights which are given to the inventor by the patent law and which he may assert against all the world through an infringement proceeding, and rights which he may create for himself by private contract, which, however, are subject to the rules of general, as distinguished from those of the patent, law. While it is true that, under the statutes as they were (and now are), a patentee might withhold his patented machine from public use, yet, if he consented to use it himself or through others, such use immediately fell within the terms of the statute, and, as we have seen, he is thereby restricted to the use of the invention as it is described in the claims of his patent, and not as it may be expanded by limitations as to materials and supplies necessary to the operation of it, imposed by mere notice to the public.

A year after the A.B. Dick case, in Bauer & Cie. v. O'Donnell, the Supreme Court began to shift its perspective by holding that, although patentees could control manufacturing, use, and sale of patented products with license agreements, they could not use license agreements to control the resale price of patented products the patentee sold. After the Motion Picture Patents case, the tide began to run more strongly against restrictive patent practices.

In 1917, the Supreme Court reversed the four-year-old Henry v. A.B. Dick Co. decision and established patent misuse as an affirmative defense to copyright infringement. In Motion Picture Patents Co. v. Universal Film Mfg. Co., the Supreme Court held that requiring a patented film projector only be used for screening films authorized by the patent holder was unenforceable and constituted patent misuse. The Court concluded that the patentee's attempt to extend its monopoly power beyond the rights that the patent statute conferred on it was inequitable, and because of the patentee's "unclean hands", the court, as a court of equity, would not grant it relief. In explaining its ruling, the Court said: