Microsoft Corp. v. AT&T Corp., 550 U.S. 437 (2007), was a United States Supreme Court case in which the Supreme Court reversed a previous decision by the Federal Circuit and ruled in favor of Microsoft, holding that Microsoft was not liable for infringement on AT&T's patent under 35 U.S.C. § 271(f).

In this case, Microsoft exported abroad the "master version" of its Windows software disk, which incorporated a speech processing function claimed by one of AT&T's patents, with the intent that such software be copied abroad for installation onto foreign-manufactured computers.

According to the Supreme Court, liability for such unauthorized replication and installation would have to arise under the patent laws of those foreign countries, not the U.S. Patent Act. Although AT&T argued that the Supreme Court's decision actually created a "loophole" for software makers to avoid liability under § 271(f), the Supreme Court explained that it is Congress, not the Court, that is responsible for addressing any such loopholes.