A public square in Amiens
Students enjoy the summer evening in the town square. One of them, Edmondo, sings a madrigal of youthful pleasure, hoping to attract the young women. They ask a brooding Des Grieux to join them, and to prove he is not cynical about love, he gallantly flirts with a group of girls with mock courtesy. As they all celebrate in the street, a carriage arrives at the inn carrying Geronte, Lescaut and his sister Manon. Des Grieux is struck by Manon’s beauty and shyly approaches her. She is called inside by her brother, but has been won over by Des Grieux’s words, and they make plans to meet later.
Geronte discusses Manon’s future with Lescaut. The family wants her to take the veil, but Lescaut has other ideas for her future, namely a match with the older Geronte (along with whatever benefits he may glean from the rich treasury official). The two men agree to meet for dinner, and Lescaut then joins a card game with the students. Edmondo overhears Geronte making plans to take Manon to Paris. He tells Des Grieux and agrees to help prevent this from happening.
Manon and Des Grieux meet as agreed and express their mutual attraction. He warns of Geronte’s plan to abduct her, so they run away together. Geronte is affronted, but Lescaut advises him to be patient, for he knows his sister’s expensive tastes will soon exhaust a student’s income.
An elegant room in Geronte’s house in Paris
As Lescaut predicted, Manon is now Geronte’s mistress and prepares for the day, aided by a hairdresser. When Lescaut arrives, she asks about Des Grieux, recalling their once-passionate affair. When speaking to Des Grieux, Lescaut has been vague about Manon’s whereabouts, but encouraged him to become a gambler so that he may acquire enough wealth to keep her in the style she requires.
Geronte has arranged a reception with musicians, who sing a madrigal in Manon’s honor. A dancing master teaches the minuet, but in spite of all the finery, Manon is bored with her new life. Realizing that she is unhappy, Lescaut privately decides to fetch Des Grieux. The guests depart for a stroll down the esplanade, and Manon promises to join them later.
Des Grieux appears at the door. He berates her lack of fidelity, but in begging forgiveness, she softens his resolve. Geronte returns and is thunderstruck to find them in each other’s arms. Manon counters his deriding remarks by holding a mirror to his face, reminding him of his advanced age. Threatening revenge, he leaves the couple alone.
Lescaut soon enters, breathless. Geronte has summoned the authorities, denouncing Manon’s lack of morality. Before fleeing with Des Grieux, she gathers her expensive jewelry, but that delay proves costly – the guards arrive and arrest her for thievery.
A square near the harbor in Le Havre
Manon is being held in the barracks, awaiting deportation to America with a group of prostitutes. Lescaut has bribed one of her jailors, and he and Lescaut wait for the changing of the guard to effect her escape. She is made aware of the plan while sharing a brief moment with Des Grieux. A shot betrays their scheme. Manon and the other prisoners are then led one-by-one to a ship while the onlooking townspeople make wicked comments as each one passes by. Des Grieux begs the captain to be hired as a deckhand, and he agrees to take the infatuated young man on the voyage to the New World.