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. It is said to have been the suggestion of producer Toru Hirayama, based on the Japanese title of Franz Kafka's Metamorphosis, which features a man transformed into an inhuman, bug-like creature against his will, a recurring theme of the Kamen Rider Series.

The first use of the phrase was by Kamen Rider 2, as the original Kamen Rider did not have a transformation call before that. It has since become an integral aspect rooted within the Kamen Rider series.

Generally, most Kamen Riders call out "Henshin!" during their transformation sequences. Variations of this phrase have been used by various Riders, either when transforming or switching between forms. These include:

Other than "Henshin" and variations of the phrase, other characters, including Riders and Rider-like characters, have used different catchphrases in a similar fashion when transforming or switching between forms. These include:

There are some Kamen Riders who do not speak or call out any phrase during their transformation. These include: