Packet Company v. Catlettsburg was a United States Supreme Court case that addressed the issue of whether a state could impose a tax on a company that was engaged in interstate commerce. The case involved the Packet Company, a company that operated a steamboat line between Cincinnati, Ohio and Catlettsburg, Kentucky. The state of Kentucky had imposed a tax on the Packet Company, which the company argued was unconstitutional because it interfered with interstate commerce. The Supreme Court held that the tax was unconstitutional because it was a direct burden on interstate commerce. The Court reasoned that the tax was a direct burden on interstate commerce because it was imposed on the Packet Company's operations in both states, and it was not a tax on the property of the company. The Court also noted that the tax was not a tax on the privilege of doing business in Kentucky, but rather a tax on the company's operations in both states. The Court concluded that the tax was unconstitutional because it interfered with interstate commerce and was a direct burden on the Packet Company's operations in both states. The Court held that the tax was invalid and that the Packet Company was not required to pay it.

In Packet Company v. Catlettsburg, the Supreme Court was asked to decide whether a state law that imposed an annual tax on steamboats and other vessels used in navigating rivers within the state violated the United States Constitution. The majority opinion held that it did not violate any constitutional provision, but Justice Field dissented from this decision. He argued that such a tax was unconstitutional because it interfered with interstate commerce by placing an undue burden on navigation between states and thus constituted an illegal interference with Congress' power to regulate interstate commerce under Article I of the Constitution. Furthermore, he argued that since there were no provisions for exemptions or deductions from this tax based upon actual use of these vessels in interstate commerce, it could be considered as having been passed solely for revenue purposes rather than regulatory ones which would also make it unconstitutional according to prior precedent set forth by Gibbons v Ogden (1824).