Magatsu or Magatsuhi in the Megami Tensei series may refer to the following:
- Magatsuhi (Nocturne), an important plot device in Shin Megami Tensei III: Nocturne.
- Magatsuhi (demon), two recurring demons in the series.
- Soulless God Oumagatsu, the boss first in Devil Summoner: Raidou Kuzunoha vs. The Soulless Army.
- Evil Order, originally "Magatsu Order" in the Japanese version of Devil Summoner: Raidou Kuzunoha vs. King Abaddon.
- Magatsu Inaba, a dungeon in Persona 4.
- Magatsu-Izanagi, a Persona in Persona 4.
Magatsuhi refers to two gods from the story of Izanagi when he had returned from in a failed mission to retrieve his late consort, Izanami. Since Yomi is the netherworld full of filth (Kegare), after his trip, Izanagi performed the ritual in order to cleanse the filth from his body. The filth that had been washed away became two gods, "Yasomagatsu Hinokami" (八十禍津日神, "Eighty Calamities God") and "Ohomagatsu Hinokami" (大禍津日神, "Great Calamity God"), known collectively as Magatsu Hinokami ( ).