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Microsoft v. AT&T, 550 U.S. 437 (2007), was a United States (U.S.) Supreme Court case that restricts the extraterritorial reach of U.S. patent law. A section of U.S. patent law, (f), lets the holder of a U.S. patent block the export from the U.S. of components that can be assembled to produce a device which violates that patent, even though the patent is not enforceable in the place where that assembly takes place. The court held that a master software disk that is exported and then used to install software at the point of assembly is not a component within the meaning of the law.

In accordance with the general principle that U.S. law stops at U.S. borders, the ruling effectively prevents holders of U.S. software patents from enforcing those patents in other countries unless they hold a valid patent there.