In the Enchanted Forest, Regina was born to the sorceress Cora and her husband Prince Henry, the fourth son of King Xavier. Growing up, Regina was terrorized by her tyrannical mother, who used magic whenever it served her.
On her sixteenth birthday, a small celebration was held in Regina's honor. Among her many gifts, Regina was presented with a beautiful mirror crafted by a renowned mirror-maker and his eighteen year-old son, named Mira. Taking an instant liking to Regina, Mira pursued her and managed to court her. The two bonded over their shared inability to please their parents; while Regina seemed unable to live up to her mother's highbrow standards, Mira did not want to follow in his father's footsteps and instead aspired to be a traveling poet, minstrel, and bard.
Over the next two years, Regina and Mira fall madly in love, but Regina opts to keep their relationship a secret, since Cora has high expectations for her daughter. At some point, Mira gifts Regina a hand mirror after she is heavily criticized by her mother, who makes several negative remarks about her physical appearance. He stated that it will allow Regina to see herself the way he has always seen her, as the fairest in all the land.
On the eve of her eighteenth birthday, Regina outrides her horseback instructor and meets Mira for a covert rendezvous. He suggests they have a romantic outing at Firefly Hill, but Regina declines since Cora is expecting her for afternoon tea in an hour. A disappointed Mira decides to instead ask Regina to marry him right there, but before he can do so, both hear a scream from a seven year-old girl on a runaway horse. Unknown to them, this girl is the princess Snow White, King Leopold's daughter, whose horse Cora had intentionally spelled in order for Regina to rescue her. Acting quickly, Regina catches up to the girl's horse and pulls her to safety. King Leopold, as Cora wished for, is so impressed by Regina's feat that he wishes to formerly thank her. Cora humbly suggests that King Leopold simply grace them with his company for the night and attends Regina's birthday celebration the following day. During Regina's birthday feast, Cora spikes King Leopold's chalice with the "curse of the empty-hearted" and he promptly proposes to Regina before all the guests. Speechless, she looks to her father for help, but he says nothing as Cora accepts on her behalf. Running to Mira later that night, Regina begs him to take her away. He agrees by giving her the ring he wanted to propose to her with early, and as they kiss, Snow White witnesses them and runs away in sadness. Regina catches up to the princess, explaining she cannot marry her father because the love she and Mira have is true. She then swears Snow White to secrecy about the relationship. The girl, however, later confesses everything to Cora in a misguided attempt to keep Regina from losing her mother as she did with hers.
On the night she and Mira were prepared to leave, Cora used magic to stop them. While Cora was furious her daughter was willing to throw being queen for a mere commoner, Regina attested that Mira makes her truly happy. Cora finally relents, seemingly coming to an understanding, and she reconciles with Regina. Mira, sympathetic to Cora's parental role, expresses gratitude for allowing her daughter's happiness. Cora, taking it upon herself to do what she believes is best for Regina, rips out Mira's heart and crushes it. In horror, Regina cradles Mira's body and weeps in despair as her mother insists true happiness will come from the power she will have as the future queen of the largest, most wealthy kingdom in the land. Sometime after this, a stoic Regina has a wedding dress fitting when Snow White mentions Cora is a good mother for understanding her and Mira's love for each other. When questioned, Snow White hesitantly admits telling Cora about Mira due to her fear that Regina would lose her mother as she herself had. Turning away from the girl, Regina reacts in shock, but she regains calm to spare Snow White's feelings. Regina lies, saying Mira ran away, but that she is happy to marry King Leopold and become her stepmother. Once Snow White exits, Cora praises Regina credit for living up to her expectations. Suspiciously, Regina questions her mother about purposely causing the princess' horse to run wild so she would save her and gain King Leopold's attention, but Cora claims she had nothing to do with it. Walking off, Regina's expression contorts into anger as she expresses regrets over not letting Snow White die on her horse. Later that night, Regina woefully gazes into the looking-glass Mira and his father crafted for her. Overwhelmed with sadness, Regina contemplates ending her life until she hears a voice come from inside the mirror. To her amazement, Mira's reflection appeared in the mirror. While Mira lost his corporeal form, his soul did not fully surrender to "the other side", allowing him to continue his existence in Regina's mirror. Fearful of what her mother would do if she discovered Mira's fate, Regina told no one of her "magic mirror".
As the wedding day approaches, Regina desperately tried to flee with the imprisoned Mira on horseback, only to be stopped ruthlessly by Cora. Following a suggestion from her father, Regina stole her mother's spell book in the hopes she could find something to help Mira. Instead she unknowingly used it to summon its creator, Rumplestiltskin. Somewhat aware of Regina's predicament, he offered to help her get rid of Cora, though Regina is against physically harming anyone, so she is given a magic traveling mirror. Rumplestiltskin instructs her to give Cora a little push into the mirror, which will then send her to another world. She questions what he wants in return, but he just vaguely confirms that someday she will do him a favor.
On the eve of her wedding, Cora steps into Regina's bedchamber and notices the looking-glass. As Regina looks into both of their reflections, Cora instructs her daughter on how to rule and to prepare to murder King Leopold so as to seize the kingdom for themselves. A horrified Regina is disgusted by her mother's words, and as she moves to give her mother a shove into the mirror, Cora magically restrains her. Cora chastises Regina for the attempt to get rid of her as Mira materializes in his glass prison to give her encouragement. Fueled by anger, Regina breaks free of the restraints and magically knocks Cora into the mirror, which then shatters into pieces. Free at last, Rumplestiltskin then magically appears and congratulates Regina. She tries to return his spellbook to him and claims magic isn't for her, but Rumplestiltskin is more interested to know how it felt to use magic. Grudgingly, Regina acknowledges that she loved it, which is all the more reason to stay away from it. She also fears becoming as magic obsessed as her mother, but Rumplestiltskin promises that is entirely up to her and not to shun magic so quickly, as it could enable her to do so much. Intrigued, Regina figured that maybe with magic and as queen she would have access to the resources needed to help her free Mira. Soon afterwards, with the hopes of reviving Mira, Regina magically enchanted his dead body to remain perfectly preserved.
After marrying King Leopold, Regina is allowed by her new husband to grow a single apple tree in the castle garden. She also brought precious little of her own material possessions to her new home, except for the mirror her lover was trapped in and thus took excessive precautions to protect it, much to the confusion of the castle staff.
The marriage is of course not one of love, as Regina still cared for her old love, Mira, and her life as queen caused her immeasurable unhappiness, as she could not bear to witness Snow White live such a charmed life after what she inadvertently did to Mira. Throughout her marriage to the king, Regina chose to poison him in secrecy in order to keep him weak and more or less bedridden so as to stave off King Leopold's romantic advances, unaware of the fact he was under her mother's love spell.
At some point in their marriage, Leopold gifts Regina a diamond encrusted brooch to show his affection for her, with the brooch having previously been a gift that he gave to his first wife Eva. Regina, however, doesn't care for the gift and regards it with little respect.
During her apprenticeship to Rumplestiltskin, Regina had great difficulty developing her skills in magic, subconsciously fearful of it due to her upbringing. During one such magic lesson, Regina is instructed by Rumplestiltskin to immobilize a black unicorn, which she manages to accomplish. However, when he orders for the animal's heart to be torn out, she balks, since doing so only reminds her of what Cora did to Mira. Disappointed, Rumplestiltskin demands that she come to terms with whatever is holding her back from learning this kind of magic. That night while conversing with Mira through the looking-glass, she gazes longingly at his preserved body and, while comforted by his remarks that she is still the fairest of them all, longed to feel his embrace.
The following week, Regina preps for another magic lesson in the Dark One's castle, but Rumplestiltskin asks what is it that she truly wants. Regina reveals that she wants to know if magic can resurrect the dead, though he claims it is impossible, a portal-jumper, Jefferson, says he knows someone from another world that can perform such a feat. She agrees to give him a royal pass to travel freely in her kingdom in exchange for transporting the person to the Enchanted Forest. After meeting the "wizard", or doctor, Victor, Regina allows him to inspect the quality of Mira's body, which he finds is in good condition for the operation. Since he needs a strong heart for surgery, she presents Victor with the vault containing her mother's collection of hearts where he picks one. One stormy night, Regina and Jefferson wait outside as Victor attempts the procedure on Mira inside a tent. Regretfully, he informs her that the resurrection was a failure. The news devastates Regina, but by the next day, she makes drastic changes after resolving to do whatever it takes to revive her true love. She witnesses Rumplestiltskin teaching magic to a new apprentice, Trish, and she proves herself more worthy by ripping out and crushing the girl's heart to ash.
With her new mindset, Regina focused all her attention on freeing Mira and grew to be a powerful sorceress. During her quest to free Mira from his glass prison, Regina used magic and the kingdom's vast wealth to maintain her youth and beauty for when she'd finally managed to revive Mira. Unfortunately, Mira started to become mentally unhinged overtime while trapped within the mirror experiencing severe boughts of amnesia and dementia; his condition progressed to the point he forgot his own name and identity. Consequently, Regina became miserable and extremely depressed over her lover's condition.
Years later, King Leopold questioned Regina's purpose in redirecting so much of the kingdom's funds for her own personal needs. Coming to the conclusion that as long as King Leopold lived she couldn't fully utilize all the kingdom's resources to help Mira, Regina upped the severity of her poison and when her husband inevitably passed away, all assumed he was striken with a mysterious illness.
During King Leopold's funeral, Regina convincingly feigned sadness over her husbands death and comforted Snow White as they both are in mourning. In truth, Regina was pleased King Leopold was gone and continued her work in being reunited with Mira. The years go by and the kingdom's wealth was squandered on Regina's pursuit to free Mira and remain lovely in his eyes. Attempting to break the Snow White's spirit out of revenge for breaking her vow of silence, Regina made her stepdaughter's life miserable by stripping the castle of everything she loved, making her wear dull dresses and banishing singing and dancing in her royal court.
When her stepdaughter turned sixteen, Mira, now a hollow spirit within the mirror, believed Snow White to be the woman he fell in love with and declared her the fairest of them all. Overwhelmed with hatred and despair over this upsetting news, Regina searches for an answer through Cora's old belongings and finds one of her mother's spells; the "curse of the empty-hearted", which can give her exactly what she desires; love as well as vengeance. The effects of the spell will force Mira to love her, but for it to work, she must take the heart of her most hated enemy — Snow White. Regina then plots in private to find a suitable person to kill her stepdaughter in secret.
When Regina hears word of a lone Huntsman having killed several men in coldblood, she believes him perfect for the job and she sends her guards to bring him to the palace. She barters with the Huntsman, promising to outlaw the slaughtering of wolves in his kingdom since he cares a great deal about their safety. In return, she asks not only for Snow White's death but for the princess' heart to be delivered to her. While he is away on this mission, Regina changes the palace to suit how she feels. The Huntsman returns with the heart of a stag instead of Snow White's, having felt pity for the innocent girl, but he hands her a farewell letter from Snow White before giving Regina the heart. Regina refuses to take it, so he attempts to read the letter until she throws the parchment into the fire. After taking the heart, she tries to magically insert it into one of the collection boxes in the vault. Nothing happens and Regina quickly catches on that the heart is not one of a human's, let alone Snow White's. Scorned by the betrayal, she tears out the Huntsman's heart as a replacement. While squeezing the heart, Regina commands that he is now hers forever and will obey her every command, starting with him killing the very wolves he sought to protect. She also warns to never cross her again, and if he does, death will be the punishment.
The Queen's black knights soon hear word of where Snow White is hiding, but by the time Regina arrives Snow White has fled. She offers a reward to whoever forfeits Snow White's location, but when none if the villagers speak up, she has her knights kill them all. Regina, upset that the citizens are loyal towards Snow White, devises a plan to get close to her and kill her. As it would take too long for her to learn a disguising spell, she asks Rumplestiltskin to change her into someone else instead. As her part of the deal, Regina agrees, on his bequest, to break off ties with King George's kingdom. Once the spell is cast, Regina becomes an old peddler woman to the outside world, but to herself, she looks the same. At the market, she stops commoners from hitting a stick effigy of her, but the Queen's knights arrive and mistake her as the creator of the effigy. As they prepare to execute her as punishment, a hooded vagrant saves her. During the battle, Regina's leg is cut with a rusty sword, and as an infection sets in, she passes out after seeing her savior is Snow White. She wakes up in a hut, where Snow White is caring for her. Regina introduces herself as "Wilma", and she expresses surprise that Snow White is helping a total stranger. While Snow White treats and bandages Regina's wound, she recalls a time when a woman saved her life, which helped her understand a connection can develop between strangers. Realizing Snow White is talking about her, Regina is moved to tears. After she is well enough to walk, Regina travels a short way with Snow White, who wished to escort "Wilma" back to a nearby village where she would be safe before taking her leave to hide from the Queen. Snow White offers her insight on the Queen, who she views as someone in constant pain, but who she believes was once good. A curious Regina asks if she would consider being a family with the Queen again, to which Snow White affirms she would if the Queen was sincere about changing. However, upon seeing the slaughtered villagers of the village she was escorting Regina to, Snow White takes back what she said, believing the Queen is evil and deserves to be punished. Regina then feigns sympathy for Snow White and offers her colorful, silky laced bodices as payment for nursing her back to health. Snow White, not wanting to hurt her feelings, accepts and Regina stifles Snow White with the enchanted ribbons. After Snow White faints, Regina attempts to use an enchanted dagger to rip out her stepdaughter's heart, but she ultimately flees the scene after seven dwarves arrive and threaten her.
Storming into Rumplestiltskin's castle, she realizes the commoners will never love her and claims that they don't matter, as she cares only to be reunited with her true love. Rumplestiltskin reverses the disguise, to which Regina gazes at her reflection and states, "Long live the Evil Queen".
Lounging in her castle, Regina receives news from her guards that they have not found Snow White, despite searching everywhere in the south and north. Even so, she presses for the search to continue. That night, she Mira shows her an image of Snow White alive and well. Regina begs Mira to reveal where she is, but Mira only offers enigmatic riddles.
The Queen's knights continue to chase after Snow White and the seven dwarves, but with the dwarves help she eludes capture once more and is rescued by a mermaid, Ariel. Regina spies on Snow White and her new companion at the Under the Sea Celebration honoring the sea goddess Ursula. Having learned to change her shape, Regina disguises herself as Ursula in order to tempt Ariel with a magic bracelet that can help her remain human, so she can be with her prince, Eric. As Regina had hoped, Ariel rushed off to find Eric and left Snow White alone and unaware of Ariel's transformation. The Queen then took Ariel's form and brushes Snow White's hair with a beautful, but poisoned comb and Snow White faints again. Ariel happens on the scene and discovers Regina's trickery too late. Though Ariel balks at the idea of leaving a friend behind, the Queen proposes that Snow White will be harmed either way and gives her the opportunity to leave unharmed with her new found legs as there will be no second chances. Once the advice is heeded, the Queen begins using magic to tear out Snow White's heart before Ariel rushes back to stab her in the neck with a fork. While Regina works to dislodge the utensil, Ariel rips the bracelet from her wrist, and the two quickly escape. Even so, the Queen gets the last laugh once she deliberately takes away Ariel's voice while the mermaid is trying to call out to her prince near his castle balcony. Regina relishes in the fact that Eric will never know Ariel's feelings for him as this outcome is far worse than being outright rejected. Regina returns to her castle, only to hear the voice of the real Ursula greeting her from the mirror. Suddenly, the statue of the sea goddess comes alive and wraps her tentacles around Regina. Regina is shocked that the goddess is real, but Ursula assures her that if she ever impersonates her again, she will find out just how real she is.
Learning from her guard that Snow White has taken refuge with the seven dwarves, and intends to sail off to some far off land, Regina intervenes in time and she prepares an apple laced with a sleeping curse, and transforms into Snow White's deceased mother, Eva, with the magic mirror the Dark One gave her. Regina (disguised as Eva) finds Snow White and convinces her to take a bite of the enchanted and poisoned apple, which seemingly kills Snow White. Ripping put Snow White's heart, Regina returns to her castle to resume her efforts to free Mira, prepares to cast her curse on him once she ressurects him. However, to her outrage, the Huntsman helped Prince Charming escape break into her palace, steal back Snow White's heart and, with help from Rumplestiltskin, Prince Charming awoke Snow White from her sleeping curse. The war which eventually ensued ended in the defeat of both Regina and her political ally King George. Devastated by her defeat and after having Mira taken from her, Regina sacrificed her father in order to enact the Dark Curse, a catastrophic curse provided by Rumplestiltskin which stripped everyone from the Enchanted Forest to the Land Without Magic.