Kiryu

is a mecha kaiju (a giant robotic monster) who first appeared in the 1974 film, Godzilla vs. Mechagodzilla. In the Showa era Godzilla films, Mechagodzilla is depicted as being constructed by extraterrestrial invaders called Simeon to confront and destroy Godzilla. In the subsequent Heisei era, Millennium era and Monsterverse films, it is usually depicted as a man-made weapon designed to defend against Godzilla and other kaiju. The character is portrayed as a robotic counterpart of Godzilla with a vast array of high-tech weaponry. Along with King Ghidorah, Mechagodzilla is commonly considered to be an archenemy of Godzilla.

Mechagodzilla was conceived in 1974 as a more serious villain than its two immediate predecessors, Gigan and Megalon, whose films were considered creative disasters. Sources stated that Tomoyuki Tanaka, Jitsuzo Horiuchi and Yasuhiro Seto first came up with the idea for the character. with director Jun Fukuda and special effects director Teruyoshi Nakano agreeing on it. According to Tanaka, Mechagodzilla was inspired by both Mechani-Kong from the previous Toho film King Kong Escapes and the robot anime genre, which was popular at the time.

Effects director Teruyoshi Nakano also felt that a mechanical monster was cheaper to construct than the mutated animals Godzilla had previously faced. As the resulting Godzilla vs. Mechagodzilla proved to be a greater critical success than previous 1970s Godzilla films, the character was revived in 1975's Terror of Mechagodzilla. The film's screenplay was based on the winning entry of a story-writing competition won by Yukiko Takayama, who continued the darker tone of the previous film by adding the subplot of Mechagodzilla being cybernetically connected to a young woman. Mechagodzilla's design remained largely unchanged from its previous appearance, though it was made to look thinner and more angular, with a darker sheen and an MG2 insignia emblazoned on its upper arms. The film's original draft was going to have Mechagodzilla destroy Tokyo utterly, though the scale of destruction was cut down for budgetary reasons.

Mechagodzilla was brought back in 1993's Godzilla vs. Mechagodzilla II, as the success of Godzilla vs. Mothra and the popularity of its main antagonist Mothra spurred Toho into reintroducing familiar characters rather than inventing new ones. Originally, the new Mechagodzilla was to be named "Berserk", and was envisioned as being a much more organic Godzilla-like creature which would later turn on its creators after becoming infected with a computer virus which makes it self-aware. Berserk would subsequently absorb more and more machinery, to the point of degenerating into a mass of metal and wires, though this concept was rejected early in pre-production.