Carpenter v. Rannels is a United States Supreme Court case that was decided in 1886. The case involved a dispute between two parties over the ownership of a piece of land in the state of Missouri. The plaintiff, Carpenter, claimed that he had purchased the land from the defendant, Rannels, and that he had paid for it in full. Rannels, however, argued that he had never sold the land to Carpenter and that he was still the rightful owner. The Supreme Court ultimately sided with Carpenter, ruling that he had indeed purchased the land from Rannels and that he was the rightful owner. The Court held that the purchase was valid and enforceable, and that Carpenter was entitled to the land. The Court also held that Rannels was not entitled to any compensation for the land, as he had not sold it to Carpenter. This decision established that a valid and enforceable purchase of land could be made without the need for a written contract.

In the case of Carpenter v. Rannels, the Supreme Court was asked to decide whether a state court had jurisdiction over an action brought by a citizen of one state against another in which it was alleged that damages were caused by fraud and deceit. The majority opinion held that such actions could not be maintained in state courts because they involved matters arising under federal law, and thus must be heard before a federal tribunal. However, Justice Field dissented from this decision on two grounds: firstly, he argued that Congress had never intended for all cases involving fraud or deceit to be tried exclusively before federal tribunals; secondly, he noted that there were no constitutional provisions preventing states from exercising their own jurisdiction over such matters. He concluded his dissent with the statement "I am unable to see any good reason why citizens should not have access to both State and Federal Courts when seeking redress for wrongs committed upon them."