Bridges v. Sperry was a United States Supreme Court case that addressed the issue of patent infringement. The case involved two inventors, William Bridges and William Sperry, who had both patented a similar device for the purpose of measuring the speed of a boat. Bridges had filed a lawsuit against Sperry, claiming that Sperry had infringed upon his patent. The Supreme Court ultimately ruled in favor of Sperry, finding that his device was not an infringement of Bridges' patent. The Court reasoned that the two devices were not substantially similar, and that Sperry's device was a new and distinct invention. The Court also noted that the two inventors had used different methods to measure the speed of a boat, and that Sperry's device was not a copy of Bridges' invention. The Court's decision in Bridges v. Sperry established the precedent that two inventions can be similar in purpose, but still be distinct inventions. This ruling has been cited in numerous subsequent patent infringement cases, and has been used to determine whether or not a patent has been infringed upon.

In Bridges v. Sperry, the Supreme Court was asked to decide whether a patentee could recover damages for infringement of their patent that occurred before they were granted the patent. The majority opinion held that such recovery was not possible because it would be unfair to allow someone who had infringed upon another's invention prior to its being patented and without knowledge of its existence, to then be liable for damages after the fact. Justice Field dissented from this decision on two grounds: firstly, he argued that Congress had intended patents should have retroactive effect; secondly, he contended that allowing pre-patent infringement claims would encourage inventors by providing them with an incentive to protect their inventions through obtaining a patent as soon as possible in order to secure any potential damages due from previous infringements.