Ex parte Mirzan is a United States Supreme Court case that dealt with the issue of whether a foreign government could be sued in a United States court. The case involved a dispute between the Ottoman Empire and Mirzan, a citizen of the Ottoman Empire. Mirzan had been arrested and imprisoned by the Ottoman Empire for alleged treason. He then sought to sue the Ottoman Empire in a United States court for damages. The Supreme Court held that the Ottoman Empire was not subject to suit in a United States court. The Court reasoned that the Ottoman Empire was a foreign government and, as such, was not subject to the jurisdiction of United States courts. The Court further reasoned that the United States had no treaty with the Ottoman Empire that would allow for such a suit. The Court's decision in Ex parte Mirzan established the principle that foreign governments are not subject to suit in United States courts unless there is a treaty or other agreement that allows for such a suit. This principle has been applied in numerous cases since then and remains an important part of United States law.

In Ex Parte Mirzan, the Supreme Court was asked to decide whether a foreign government could be sued in an American court. The majority opinion held that it could not, as such suits would violate international law and interfere with diplomatic relations between nations. Justice Field dissented from this decision on the grounds that Congress had passed legislation allowing for such suits against foreign governments when they were based on contracts made by those governments within the United States. He argued that since Congress had authorized these types of lawsuits, it should be up to them rather than the courts to determine if any particular suit violated international law or interfered with diplomatic relations. In his view, denying individuals their right to sue a foreign government simply because of its status as a sovereign nation was contrary both to justice and common sense.