Ruiko Saten is a character in the comic A Certain Scientific Railgun and its derivative works. She also appears in A Certain Magical Index: The Movie – The Miracle of Endymion.
She is a one grader in Sakugawa Middle School. With long hair decorated with white flowers. Though looks like to be an optimistic and simple person, she is very sensitive to feelings of people around. She is obsessive with Kazari Uiharu's dress.