What was the title of the Inquisition's prosecutor?

The Inquisition’s prosecutor was called the fiscal.

The fiscal was a legal officer of each inquisitorial tribunal. The role included preparing accusations, investigating denunciations, questioning witnesses, and managing the prosecution’s case during inquisitorial proceedings.

The office worked alongside several other officials. Inquisitors directed the tribunal, calificadores—usually theologians—assessed whether conduct constituted a crime against the faith, and the alguacil handled arrests, imprisonment, and other enforcement duties. The fiscal’s function was therefore prosecutorial rather than judicial or theological.

“Fiscal” can cause confusion because in modern Spanish-speaking legal systems it often still means a public prosecutor. It does not mean “inquisitor”: inquisitors presided over the tribunal and issued judgments, while the fiscal presented the case. Nor was the fiscal the defendant’s lawyer; inquisitorial defendants did not have a modern adversarial defense system.