Weightman v. Caldwell was a case heard by the United States Supreme Court in 1819. The dispute arose when William Weightman, an attorney from Pennsylvania, sued James Caldwell of New Jersey for failing to pay him $1,000 for legal services he had provided on behalf of Caldwell's son-in-law. Weightman argued that he should be paid according to the terms of their agreement and sought damages for breach of contract. The Supreme Court ultimately ruled in favor of Weightman and held that contracts must be honored unless there is some valid reason not to do so; thus, it found that Caldwell was liable for breaching his contractual obligation with Weightman and ordered him to pay the full amount owed plus interest. This decision established important precedent regarding contract law in America as it affirmed the principle that parties are legally obligated to fulfill their agreements or face consequences if they fail to do so.

In Weightman v. Caldwell, the Supreme Court was asked to decide whether a state court had jurisdiction over a case involving citizens of different states. The majority opinion held that it did not have such jurisdiction and dismissed the appeal. Justice Story dissented from this decision, arguing that there is no constitutional provision which prevents state courts from exercising their authority in cases between citizens of different states when those parties are present within its boundaries and voluntarily submit themselves to its laws. He further argued that if Congress has not expressly prohibited such suits then they should be allowed as long as both parties agree to abide by them; otherwise, he feared it would lead to an unjust situation where one party could take advantage of another due to differences in state laws or regulations regarding contracts or other matters related thereto.