A writ of coram nobis (also writ of error coram nobis, writ of coram vobis, or writ of error coram vobis) is a legal order allowing a court to correct its original judgment upon discovery of a fundamental error that did not appear in the records of the original judgment's proceedings and that would have prevented the judgment from being pronounced. The term coram nobis is Latin for "before us" (i.e., the king) and the meaning of its full form, quae coram nobis resident, is "which [things] remain in our presence". The writ of coram nobis originated in the courts of common law in the English legal system during the sixteenth century.

The writ of coram nobis still exists today in a few courts in the United States, where it applies only to criminal proceedings, not civil ones. In 1907, the writ became obsolete in England and replaced by other means of correcting errors; however, the writ survives in the United States in various forms in the federal courts, in the courts of sixteen states, and the District of Columbia courts. For those courts with the authority to issue a writ of coram nobis, the rules and guidelines differ – sometimes significantly. Each state is free to operate its own coram nobis procedures independent of other state courts as well as the federal court system. In other words, the criteria required to issue the writ in one state (or federal) court system are different from the criteria required to issue the writ in a different court system. A writ can be granted only by the court where the original judgment was entered, so those seeking to correct a judgment must understand the criteria required for that specific court.