Japan, early 20th century. Lieutenant B.F. Pinkerton of the U. S. Navy inspects a house overlooking Nagasaki harbor that he is leasing from Goro, a marriage broker. The house comes with three servants and a geisha wife named Cio-Cio-San, known as Madame Butterfly. The lease runs for 999 years, subject to monthly renewal. The American consul Sharpless arrives breathless from climbing the hill. Pinkerton describes his philosophy of the fearless Yankee roaming the world in search of experience and pleasure. He is not sure whether his feelings for the young girl are love or a whim, but he intends to go through with the marriage ceremony.
Sharpless warns him that the girl may view the marriage differently, but Pinkerton brushes off such concerns and says someday he will take a real, American wife. He offers the consul whiskey and proposes a toast. Butterfly is heard climbing the hill with her friends for the ceremony. In casual conversation after the formal introduction, Butterfly admits her age, 15, and explains that her family was once prominent but lost its position, and she has had to earn her living as a geisha. Her relatives arrive and chatter about the marriage. Cio-Cio-San shows Pinkerton her very few possessions, and quietly tells him she has been to the Christian mission and will embrace her husband’s religion. The Imperial Commissioner reads the marriage agreement, and the relatives congratulate the couple. Suddenly, a threatening voice is heard from afar—it is the Bonze, Butterfly’s uncle, a priest. He curses the girl for going to the Christian mission and rejecting her ancestral religion. Pinkerton orders them to leave and as they go the Bonze and the shocked relatives denounce Cio-Cio-San. Pinkerton tries to console Butterfly with sweet words. She is helped by Suzuki into her wedding kimono, and joins Pinkerton in the garden, where they make love.
