- one of the series' main heroines, as well as the main protagonist of the side story, A Certain Scientific Railgun. Her parents are Tabigake and Misuzu Misaka, which her father is a prominent businessman and millionaire. Despite her rich background, she grew up in a normal typical childhood.
- At a young age, she was discovered to be a Level 1 Electromaster, espers who have the ability to generate and control electricity. She enrolled into Academy City to train her powers and worked very hard until her powers were ranked Level 5, the highest esper ranking, with her being the third strongest of the seven espers with this rank. As an electromaster, she can generate and manipulate electricity which she can use to shock opponents, hack into electronics like computer networks and security systems, and use electromagnetism to cling to surfaces or manipulate iron particles into a chain-sword whip. Mikoto's signature move is her ability to shoot metal projectiles such as coins at high destructive speeds, hence her nickname, "The Railgun". If she is in a bad mood, she will sometimes let out bursts of electricity describing her emotional stress, usually resulting in power failures or even citywide blackouts.
- Mikoto attends Tokiwadai Middle School, a famous girls' school for the rich and elite psychics and one of the five elite schools of Academy City. To most people, she is considered a proper lady, but in reality, she has a short-tempered, prideful, and improper attitude with some tomboyish tendencies and insecurities, a fact few other characters know. She is fond of cute, childish things, such as flowery pajamas and Gekota, the popular frog mascot franchise.