Bloom was an ordinary girl living on Earth until she encountered a girl fighting a yellow ogre, Knut. The girl, Stella, turned out to be the princess of the planet Solaria and a fairy. Stella believed that Bloom had magical powers within her, because during the fight with the ogre, Bloom uncontrollably unleashed a blast of light. Stella took Bloom with her to Magix, in the Magical Dimension, where they enrolled in Alfea, a school for fairies. At first, Bloom was enrolled as a princess who was not coming to Alfea because Bloom was not on the admittance list. After Stella accidentally tells their friends that Bloom is actually from Earth, Alfea's Headmistress, Ms. Faragonda, allow her to stay because she is still a fairy and wishes to learn about magic.
Bloom and Stella are joined by new friends: Flora, who is a shy girl who loves nature, having nature-related powers, an intelligent girl Tecna who has a love for technology, having technologically-based powers and Musa, a tomboyish girl who loves music, having musical powers. They, along with Bloom and Stella, form the Winx Club, the word "winx" being a pun on the word "wings." Eventually, Bloom discovers her powers and the Winx girls are confronted by the Trix, a trio of witches. The witches, Icy, Darcy and Stormy, are students at Cloudtower, an all-female school for witches. Icy sought to find the Dragon's Flame, Magix's most powerful magic, coming from a deity in the series. The girls also become friends with four students from Redfountain, an all-boys school that trains them to become Specialists, warriors who can use a differing range of weapons along with other abilities. They are Sky, Brandon, Timmy and Riven.
During the season, the Trix unleash constant traps to defeat the Winx girls and get the Dragon's Flame. The turning point came in episode 17, when Bloom discovered that Brandon and Sky had switched identities in order to protect the other. Upset, Bloom returns to Earth, with the Trix secretly following. There, Bloom discovers her true identity - she is the princess of the planet Domino, and when it was destroyed by the three Ancestral Witches, baby Bloom was sent to Earth by her older sister, Daphne, and was adopted by her Earth parents. Alas, the Trix attacked Bloom on Earth and took the Dragon's Flame, leaving Bloom completely powerless. With the Flame in their possession, the Trix used it to summon the Army of Darkness, an endless militia of insect monsters who regenerate when destroyed. At Alfea, the students struggled to fight them, but to no avail. Figuring the only way to defeat the Trix is with a power equal to the Flame, the Winx Club travel to Domino to claim any remnants of the Dragon's Flame.
On Domino, the Winx girls are immediately attacked by vicious monsters, but manage to hold up in the ruined palace that once belonged to Bloom's family. Guided by the ethereal appearance of her sister Daphne, Bloom is told about final moments of her planet. After the destructive conquest by three ancient witches to seize the Dragon's Flame, Bloom's parents, Oritel and Marion, endowed the infant Bloom with a small portion of it. She was handed off to her sister for safekeeping, while their parents used desperate measures to eliminate the witches. Oritel and Marion seemingly sacrificed themselves by using the full power of the Dragon's Flame, rendering their planet inhospitable. Daphne supposedly used the last of her magical endowments to send Bloom to Earth. The bestiary of Domino eventually overran the palace forcing the Winx Club to retreat without any information on how to re-acquire the Flame.
The Winx Club proceed with a secondary plan to take it from the Trix, who have now conquered Cloudtower and turned it into their base of operations. The Army of Darkness quickly overpower the Winx Club and their specialist support, and they are once again are forced to retreat. While falling back to campus of Alfea, Daphne guides Bloom to a nearby lake where she appears and explains to her that the Dragon's Flame can never be taken from her. By sheer willpower, Bloom regenerates her powers.
The final battle begins at Alfea, and with the Dragon's Flame, Bloom squares off in a duel against Icy, while the others take on Darcy and Stormy. The Trix each have a share of the Dragon's Flame, so when Darcy and Stormy are defeated, most of the monsters disappear, leaving only Icy to be defeated by Bloom. After the battle, the Trix are sent to theFortress of Light, a temple, as punishment, while a celebration is held back at Alfea. The Winx girls, Mirta, Knut and the Specialists toast to the new year. The Winx's journey has just begun...