Reybold v. United States was a case heard by the United States Supreme Court in 1875. The case involved a dispute between the United States and the Reybold family over the ownership of a parcel of land in Delaware. The Reybolds claimed that they had purchased the land from the United States in 1845, but the United States argued that the sale was invalid because the land had been previously granted to another party. The Supreme Court ultimately sided with the United States, ruling that the Reybolds had not acquired valid title to the land. The Court held that the United States had not intended to convey title to the Reybolds, and that the Reybolds had not taken the necessary steps to perfect their title. The Court also held that the United States had the right to reclaim the land, as it had not been validly conveyed to the Reybolds. The decision in Reybold v. United States established the principle that the United States has the right to reclaim land that has been improperly conveyed. The decision also established that the United States has the right to reclaim land that has been granted to another party, even if the grantee has taken steps to perfect their title.

In Reybold v. United States, the Supreme Court was asked to decide whether a patent for an invention of a machine used in making paper bags could be revoked due to fraud on the part of the inventor. The majority opinion held that because there had been no proof presented that any fraudulent acts were committed by the inventor, and since patents are presumed valid until proven otherwise, it would not be appropriate to revoke this particular patent. Justice Field dissented from this decision arguing that when an applicant makes false statements or omits material facts during their application process then they should not receive protection under federal law as provided by a patent grant. He argued further that if such behavior is allowed then it will encourage others to make similar misrepresentations with impunity and thus undermine public confidence in our nation's intellectual property laws.