Frankenstein's Monster or simply Frankenstein, (フランケンシュタイン), is a kaiju that is based of the original creature from the 1818 horror novel Frankenstein; or, the Modern Prometheus by Mary Shelley.
kaijin interpretation of the character appears in the 1965 Toho film, Frankenstein vs. Baragon. After the atomic bomb which destroyed Hiroshima irradiated his immortal heart, it slowly regrew into a feral boy, and eventually a giant. Frankenstein became an outcast, blamed for the crimes of the underground monster Baragon and hunted by the JSDF. Ultimately, he confronted and killed the monster before a sudden fissure sent him plummeting into Earth's depths, his fate unknown. Though referenced in The War of the Gargantuas as the ancestor of Sanda, Toho's Frankenstein has not appeared in any media since then.