Rainbow Dash is a sky-blue pegasus pony with magenta eyes, and a rainbow-colored mane and tail. Her cutie mark is a cloud with a red, yellow and blue lightning bolt. She is very brave, bold and tomboyish; and though she often appears arrogant, she still has a kind heart and is there for her friends when they need her.[5] She thought reading is for "eggheads" like Twilight until "Read it and Weep". She is fast and works with the other pegasi to move clouds to control the weather. Her lifelong dream is to join the Wonderbolts, Equestria's aerobatic flight team, and she has been accepted into their training program and selected as cadet team leader.[9] Rainbow Dash's signature move is the Sonic Rainboom, in which she flies fast enough to break the sound barrier, creating a sonic boom and a rainbow-hued shock wave. She works as head of the weather team in Ponyville.

"The Cutie Mark Chronicles" reveals that when she performed this move for the first time in a race for Fluttershy's honor, she earned her cutie mark and set in motion a chain of events that allowed the other five main characters to earn theirs as well.[8] She represents the Element of Loyalty. In "May the Best Pet Win!", while trying to decide on a pet, she is saved from an avalanche by a tortoise and decides to keep him, naming him Tank. She equips him with a helicopter rotor so that he can fly and keep up with her, though he is very clumsy in the air as demonstrated in "Just for Sidekicks".