Kellogg Co. v. National Biscuit Co., 305 U.S. 111 (1938), is a United States Supreme Court case in which the Court ruled that the Kellogg Company was not violating any trademark or unfair competition laws when it manufactured its own Shredded Wheat breakfast cereal, which had originally been invented by the National Biscuit Company (later called Nabisco).

The Court therefore "forcefully applied the principle that once a patent has expired, its benefits are to be freely enjoyed by the public.

The Kellogg Company started manufacturing shredded wheat cereal in 1912 after Perky's patents expired; after the Shredded Wheat Company objected, Kellogg stopped manufacturing their version in 1919.

On the protection of the cereal's shape, the Court decided that the shape was functional and that there was a right to copy it after its patent expired, as the use of unfair competition and trademark laws could otherwise be used to impede the ability of rivals to create any competitive product, even though the patent had expired.

On the picture of the two shredded wheat biscuits in the bowl of milk, the Court noted that "the name Kellogg was so prominent on all of the defendant's cartons as to minimize the possibility of confusion", and hence there was no fraudulent "passing off" of Kellogg's cereal biscuits as having been created by Nabisco.