Power of a court to allow
lawsuits to be originated in that court. As opposed to "appellate"
jurisdiction, which accepts cases only on appeal from the court with "original"
jurisdiction. The court with "original
jurisdiction" is the court where
trial happens.
Article III, Section 2 of the Constitution of the United States provides:
In all cases affecting ambassadors, other public ministers and consuls, and those in which a State shall be a party, the Supreme Court shall have original jurisdiction.
The practical effect of this is ameliorated by a statute, 28 U.S.C. § 1251, which limits the original and exclusive jurisdiciton of the Supreme Court to cases between States. An example would be Texas v. New Mexico 494 U.S. 111 (1990); 485 U.S. 388 (1988); 482 U.S. 124 (1987); 462 U.S. 554 (1983); 446 U.S. 540 (1980) (a water rights controversy). Even where the Supreme Court retains original and exclusive jurisdiction, it does not necessarily conduct trials. In Texas v. New Mexico for example, the Court appointed a Tenth Circuit judge, an expert on western water law, to be a “Special Master” and hear the evidence in the case.
In all other cases, while the Supreme Court has original jurisdiction, Congress has also granted original jurisdiction to the trial courts which Congress has created, the United States District Courts.
Section 1251 provides:
(a) The Supreme Court shall have original and exclusive
jurisdiction of all controversies between two or more States.
(b) The Supreme Court shall have original but not exclusive
jurisdiction of:
(1) All actions or proceedings to which ambassadors, other
public ministers, consuls, or vice consuls of foreign states are
parties;
(2) All controversies between the United States and a State;
(3) All actions or proceedings by a State against the citizens
of another State or against aliens.