Mont-Tonnerre is the name of a département of the First French Republic and later the First French Empire in present Germany. It is named after the highest point in the Rhenish Palatinate, the Donnersberg. It was the southernmost of four départements formed in 1798, when the west bank of the Rhine was annexed by France. Prior to the French occupation, its territory was divided between the Archbishopric of Mainz, the Bishopric of Speyer, the Bishopric of Worms, the Nassau-Weilburg, the Hesse-Darmstadt and the Electorate of the Palatinate. Its territory is part of the present German states of Rhineland-Palatinate and Saarland. Its capital was Mainz (French: Mayence). The département was subdivided into the following arrondissements and cantons (situation in 1812):
- Mainz, cantons: Alzey, Bingen, Bechtheim, Kirchheimbolanden, Mainz (2 cantons), Nieder-Olm, Ober-Ingelheim, Oppenheim, Wöllstein and Wörrstadt.
- Kaiserslautern, cantons: Göllheim, Kaiserslautern, Lauterecken, Obermoschel, Otterberg, Rockenhausen, Winnweiler and Wolfstein.
- Speyer (French: Spire), cantons: Dürkheim, Edenkoben, Frankenthal, Germersheim, Grünstadt, Mutterstadt, Neustadt, Pfeddersheim, Speyer and Worms.
- Zweibrücken (French: Deux-Ponts), cantons: Annweiler, Homburg, Landstuhl, Medelsheim, Neuhornbach, Pirmasens, Waldfischbach and Zweibrücken.
Its population in 1812 was 342,316.