*Elizabeth "Betty" Barrett (a.k.a. Atomic Betty) is the show's titular protagonist.

On her home planet Earth, to most of her friends and family, Betty Barrett is an average 7th-grade middle school student who is highly athletic and loves every single sport that she tries, especially ice hockey and ice skating. She even enjoys singing in her band.

Betty is a Canadian girl with fair skin, long red hair with straight bangs, and lime-green eyes. She usually styles her hair in a ponytail, although when wearing certain outfits, such as her swimwear or winter coat, she lets her hair down, revealing that it is waist-length. When she was younger, she used to style her hair in pigtails in the past as her hair was still short at the time. She also wore an outfit the same colors as her usual clothes which consists of a yellow T-shirt, green overalls with pockets, white socks, and black mary-janes along with a similar headband.

As a civilian on Earth, her usual outfit consists of a white long-sleeved collared shirt, which is worn underneath a yellow V-neck long-sleeve sweater with green stripes on the sleeves and a green line on the V-neck. She also wears a green knee-length skirt, white socks, and black and white tennis shoes. She also wears a green headband for her hair.

At night, her bedtime outfit consists of a pale pink nightgown with long, puffy sleeves, frills decorating the collar and wrists, and pale pink slippers. She also wears a pink headband for her hair.

When she's not in bed, she wears a deep pink bathrobe with white trim and deep pink slippers.

When going for a dip, she wears a pink and white-striped bathing suit, although a swimcap and goggles might be optional.

When on a Galactic Guardian mission as Atomic Betty, she wears her standard Galactic Guardian uniform, which consists of a white headdress, a pink dress with a tutu-esque skirt, white gloves, a white belt with an atom symbol, and white thigh-high go-go boots. She also wears red lipstick.

Betty is a very smart, joyful, funny, strong-willed, tough, pleasant and a very independent young girl with highly eccentric interests and is not afraid to speak her mind on any subject. She also has a bit of a temper, and can get easily annoyed, most often by her rival Penelope Lang.

On Earth, she likes playing pranks, listening to music, reading her sci-fi comics, popping an Ollie on her skateboard, hanging with her best friends Noah and Paloma, and daydreaming about her crush, Dylan.

In space, she loves protecting the galaxy with her gang, flying in her star cruiser and fighting treacherous galactic supervillains.

Throughout the first season of the show, Betty thinks that she is the only human ever to be chosen to be a Galactic Guardian, until she discovers that her grandmother was a retired Galactic Guardian named Beatrixo, as well as one of the first Galactic Guardians.

Whenever there is trouble in outer space, she is called on by her commanding officer, Admiral DeGill, and along with her crew, is the captain of her own star cruiser under her secret identity of Atomic Betty, who is considered throughout the galaxy as a well-known and quite famous Galactic Guardian and the Defender of the Cosmos.

In outer space, she and her crew, a food-loving, green-skinned alien named Sparky and a robot named X-5, investigate various intergalactic crimes and fight evil super villains. An expert hand-to-hand fighter, kick boxer, an expert in karate, Betty can easily defend herself against most of her opponents, but is also equipped with a special Galactic Guardian-issued utility bracelet, which houses other technological devices, such as a holographic communicator she uses to speak to Admiral DeGill and her crew, remote controls for her star cruiser and its teleporter, as well as an arsenal of gadgetry and weaponry to use on her missions.

Personality Smart, joyful, clever, cute, kind, friendly, funny, strong-willed, tough, pleasant, brave, independent, heroic, tomboyish, beautiful, charming, short-tempered (sometimes), athletic, average, highly eccentric*