McGee v. Mathis was a United States Supreme Court case that dealt with the issue of whether a state court had the authority to enforce a contract made in another state. The case involved a dispute between two parties, McGee and Mathis, over a contract made in the state of Mississippi. McGee had agreed to pay Mathis a certain sum of money in exchange for a tract of land in Mississippi. Mathis then sued McGee in a state court in Louisiana, seeking to enforce the contract. The Supreme Court held that the state court in Louisiana did not have the authority to enforce the contract made in Mississippi. The Court reasoned that the contract was made in Mississippi and was therefore subject to the laws of that state. The Court further held that the state court in Louisiana could not enforce the contract because it was not made in Louisiana and was not subject to the laws of that state. The Court's decision in McGee v. Mathis established the principle that a state court cannot enforce a contract made in another state. This principle has been applied in numerous cases since then, and it remains an important part of contract law today.

In McGee v. Mathis, the Supreme Court was tasked with deciding whether a contract between two parties that had been made in one state but performed in another could be enforced by the courts of the latter state. The majority opinion held that such contracts were not enforceable under federal law and thus could not be enforced by any court. However, Justice Field dissented from this ruling, arguing that since Congress had granted to each state authority over its own laws and regulations regarding contracts within their borders, it would follow logically that states should also have jurisdiction over those same contracts when they are performed outside of their boundaries as well. He argued further that if states did not have this power then citizens would suffer great injustice due to being unable to enforce valid agreements made across different jurisdictions.