United States v. Wrightwood Dairy Co., 315 U.S. 110 (1942), was a major decision of the US Supreme Court upholding the Agricultural Marketing Agreement Act of 1937 as a valid use of Congress' authority under the Commerce Clause of the United States Constitution.

However, the federal government claimed that Wrightwood Dairy was acting in competition to interstate businesses and should therefore be subject to its marketing orders and agreements.

If allowed to continue purchasing raw milk from Illinois farms at less than the USDA's price floor, Wrightwood Dairy would be capable of selling its processed milk at prices lower than its competitors engaged in interstate business, thereby threatening the regulatory scheme.

However, the Supreme Court found that Congress only altered its phrasing to comply with the 1935 verdict in A.L.A.

[1] The Michigan Law Review interpreted this decision as effectively reversing the Supreme Court's 1941 ruling in Federal Trade Commission v. Bunte Brothers, Inc., which had narrowly interpreted the Federal Trade Commission Act of 1914 as limiting the Federal Trade Commission's regulatory oversight to interstate businesses.