Yale Lock Manufacturing Company v. Greenleaf was a United States Supreme Court case in which the Court held that a patentee of a lock was entitled to damages for the infringement of his patent by another party. The plaintiff, Yale Lock Manufacturing Company, had obtained a patent for a lock and had sold the lock to the defendant, Greenleaf. Greenleaf then made and sold a lock that was substantially similar to the plaintiff's patented lock. The plaintiff sued Greenleaf for infringement of its patent. The Supreme Court held that the plaintiff was entitled to damages for the infringement of its patent. The Court reasoned that the patentee was entitled to the exclusive right to make, use, and sell the patented invention, and that the defendant had infringed upon that right by making and selling a lock that was substantially similar to the plaintiff's patented lock. The Court also held that the plaintiff was entitled to damages for the infringement, as the defendant had profited from the sale of the infringing lock. In conclusion, the Supreme Court held that the plaintiff was entitled to damages for the infringement of its patent by the defendant. The Court reasoned that the patentee was entitled to the exclusive right to make, use, and sell the patented invention, and that the defendant had infringed upon that right by making and selling a lock that was substantially similar to the plaintiff's patented lock. The Court also held that the plaintiff was entitled to damages for the infringement, as the defendant had profited from the sale of the infringing lock.

In Yale Lock Manufacturing Company v. Greenleaf, the Supreme Court was tasked with determining whether a patentee of an invention could recover damages for infringement when the defendant had not used any part of the patented device but instead created a similar product using different components. The majority opinion held that such recovery was not possible because it would be unfair to grant exclusive rights in perpetuity over all devices which perform substantially the same function as those described in a patent regardless of their composition or construction. Justice Field dissented from this decision and argued that Congress intended to protect inventors by granting them exclusive rights over their inventions and allowing them to seek compensation if another person infringed upon these rights without authorization. He further noted that while there may have been some differences between the two products, they were still performing essentially identical functions and thus should both be subject to protection under existing laws governing patents.