After the Overture, the citizens of Oz enter to celebrate the death of the Wicked Witch of the West ("No One Mourns the Wicked"). Glinda descends onto stage to confirm the circumstances of the Witch's melting by Dorothy. The scene shifts to the birth, years earlier, of the green-skinned Elphaba Thropp, daughter of the governor of Munchkinland. Elphaba suffers an unhappy childhood, facing discrimination because of her skin color and only being raised by her widowed father. At Shiz University, Elphaba first encounters Galinda, a spoilt and popular Uplander ("Dear Old Shiz"). In a moment of anger, as she is told that she will be rooming with Galinda, Elphaba reveals an innate magical talent. This impresses Madame Morrible, the headmistress of Shiz, who notes that Elphaba's talents may be of use to the Wizard of Oz ("The Wizard and I"); she promises to give Elphaba private sorcery classes. Galinda is jealous and takes an immediate dislike to Elphaba; Elphaba takes a similar dislike to Galinda ("What Is This Feeling?").
Doctor Dillamond, a Goat and Shiz University's only Animal professor, is teaching history class when it is interrupted by an anti-Animal slogan on the back of his blackboard. After dismissing the class, he confides in Elphaba that something is causing the Animals of Oz to lose their powers of speech ("Something Bad"). Fiyero, a Winkie prince, arrives at Shiz and immediately impresses his own brand of cavalier, carefree living on the students ("Dancing Through Life").
Fiyero organizes a party at a local ballroom; while preparing for the dance, Galinda discovers a black pointed hat in a box and gives it to Elphaba as a 'present'. Galinda convinces a munchkin student named Boq to take Nessarose (Elphaba's wheelchair-bound sister) to the party, more to avoid unwanted attention from Boq than out of any desire to be kind. Nessarose has a crush on Boq and is so overjoyed to be invited that she asks Elphaba if there is any way to repay what she perceives as Galinda's kindness. At the dance, Galinda is surprised by the appearance of Madame Morrible, who gives her a training wand and tells her that Elphaba has insisted she be included in the sorcery seminar. Clearly, despite apparent misgivings, Elphaba has done as her sister requested and found something nice to do for Galinda. Elphaba arrives wearing the hat Galinda had given her, only to be ridiculed. Defiant, she proceeds to dance alone and without musical accompaniment. Feeling guilty, Galinda joins Elphaba on the dance floor, marking the start of a new friendship between the two. After the dance, Galinda and Elphaba talk in their room. Elphaba confides that her father hates her because of her green skin and had forced her mother to eat milk flowers to ensure that Nessarose was not born the same, causing Nessarose to be born early, crippling her and killing their mother. Moved by a desire to help her new friend, Galinda decides to give Elphaba a makeover and to make her popular ("Popular").
The next day, Ozian officials take Doctor Dillamond away. The new history teacher arrives with a frightened lion cub in a cage, revealing that Animals that are kept in cages will never learn to speak. Outraged, Elphaba casts a freezing spell over the whole class except for Fiyero, and together they steal the cub and set it free. There is a hint of chemistry between the two, but Fiyero leaves, embarrassed. It begins raining, and Elphaba takes refuge under a bridge and regrets that it would be impossible for someone like Fiyero to love someone like her ("I'm Not That Girl"). Madame Morrible finds Elphaba and announces that she has been granted an audience with the Wizard. At the train station, Galinda and Fiyero see Elphaba off to the Emerald City. Galinda complains to Elphaba privately that Fiyero's affections toward her seem to be waning. In an attempt to impress Fiyero, Galinda announces that she will change her name to "Glinda" in honor of Doctor Dillamond's persistent mispronunciation. Fiyero does not appear to notice and, feeling bad for Glinda, Elphaba invites her along to see the Wizard.
After a day of sightseeing in the Emerald City ("One Short Day"), Elphaba and Glinda meet the Wizard. Eschewing the special effects which he employs for the benefit of most visitors, he invites Elphaba to join him ("A Sentimental Man"). As a test, he asks that Elphaba give his Monkey servant, Chistery, the ability to fly using the Grimmerie, an ancient book of spells. Elphaba demonstrates an innate understanding of the lost language and successfully gives Chistery wings. The Wizard reveals an entire cage full of monkeys who now also have wings because of Elphaba's spell, and remarks that they will make good spies to report any subversive Animal activity. Realizing that she has been used and that the Wizard has no power of his own, Elphaba runs away with the Grimmerie, pursued by the palace guards.
Defying Gravity
Elphaba and Glinda run into the tallest tower, where they hear Madame Morrible declaring to all of Oz that Elphaba is a "Wicked Witch" and is not to be trusted. Falling to the floor, Elphaba enchants a broomstick to fly and tries to convince Glinda to join her in her cause, but Glinda cannot resist the call of popularity and refuses. Leaving Glinda behind, Elphaba rises into the sky on the broomstick, promising to fight the Wizard with all her power. ("Defying Gravity").
