Texaco Inc. v. Dagher, 547 U.S. 1 (2006), was a decision by the Supreme Court of the United States involving the application of U.S. antitrust law to a joint venture between oil companies to market gasoline to gas stations.

The Court ruled unanimously[1] that the joint venture's unified price for the two companies' brands of gasoline was not a price-fixing scheme between competitors in violation of the Sherman Antitrust Act.

The formation of Equilon was approved by consent decree, subject to certain divestments and other modifications, by the Federal Trade Commission,[2] as well as by the state attorneys general of California, Hawaii, Oregon, and Washington.

After Equilon began to operate, a class of 23,000 Texaco and Shell gas station owners filed a class action lawsuit in the United States District Court for the Central District of California, alleging that, by unifying gasoline prices under the two brands, petitioners had violated the per se rule against price fixing that the Supreme Court had long recognized under § 1 of the Sherman Act.

Contrary to the Ninth Circuit's ruling, the Court did not believe that the ancillary restraints doctrine applied because the challenged business practice involved the "core activity" of the joint venture—the pricing of the goods it produced and sold.