|This article is about a/an common trend in the Kamen Rider Series.|
"Henshin!" (変身 Henshin) is the Japanese word for "transformation/transform" meaning "to change or transform the body" or "equip". In the Kamen Rider Series, it is a common transformation call for what a Rider shouts when they are about to transform, as it might have been a word that Shotaro Ishinomori himself invented.
With the exception of the wordless transformations of Riderman, the riders of Kamen Rider The First & Kamen Rider The Next, the Oni Kamen Riders in Kamen Rider Hibiki, and Shin in Shin Kamen Rider: Prologue, the "A - ma - zon!" cry of Kamen Rider Amazon, and the "Set up!" call of Kamen Rider X, every Japanese Kamen Rider uses the phrase when assuming Rider Form.
Some Riders have similar catchphrases for when they assume different forms while still in rider form, such as Kamen Rider Kuuga's "Cho Henshin" (超変身 Chō Henshin, lit. "Super Transformation") phrase.