The Mezentian Gate is the third novel in the Zimiamvian Trilogy by Eric Rücker Eddison. It is primarily a history of the rule of the fictional King Mezentius (the Tyrant of Fingiswold), and his methods of gaining and holding the Three Kingdoms of Fingiswold, Meszria and Rerek in sway.
Published posthumously, The Mezentian Gate is only partially completed as prose. In many of the central chapters, only the plot outline is presented.
The Mezentian Gate is chronologically the first book in the Zimiamvian Trilogy.