International Salt Co. v. United States, 332 U.S. 392 (1947), was a case in which the United States Supreme Court held that the Sherman Act prohibits as per se violations all tying arrangements in which a product for which a seller has a legal monopoly, such as a patent, requires purchasers to buy as well a product for which the seller has no legal monopoly.

The US government brought a case charging the company of an antitrust violation by the tying of its products.

The defendant replied to the charges with the contention that the tying arrangement was necessary to control the quality of salt being used in its machines and claimed that salt not meeting certain standards would damage the machines.

The Supreme Court was asked to determine whether such an arrangement was a per se violation of the antitrust laws.

The defense that customers could buy elsewhere if other vendors sold at lower prices was also rejected since the defendant could foreclose the market simply by meeting it.