An inquisitor was an official in an Inquisition, an organisation or program intended to eliminate heresy and other things frowned on by the Roman Catholic Church. Literally, an inquisitor is one who "searches out" or "inquires" (Latin inquirere < quaerere, "to seek").

The chief inquisitor of an Inquisition was often called the Grand Inquisitor.

Prominent inquisitors

Some of the more well-known inquisitors throughout history include:

• Arnaut Catalan
• Bernard Gui
• Diego Deza
• Fabio Chigi (later Pope Alexander VII)
• Heinrich Institoris, author of Malleus Maleficarum
• Francisco Jimenez de Cisneros
• Francisco Peña
• James Sprenger, possible co-author of Malleus Maleficarum
• Konrad von Marburg
• Pedro de Arbués
• Tomás de Torquemada
• Nicolau Aymerich author of Directorium Inquisitorum
• Sebastien Michaelis