Violetta Valéry, a famed courtesan, throws a lavish party at her Paris salon to celebrate her recovery from an illness. Gastone, a viscount, has brought with him a friend, Alfredo Germont, a young bourgeois from a provincial family who has long adored Violetta from afar. While walking to the salon, Gastone tells Violetta that Alfredo loves her, and that while she was ill, he came to her house every day. Alfredo joins them, admitting the truth of Gastone's remarks. Baron Douphol, Violetta's current lover, waits nearby to escort her to the salon; once there, the Baron is asked to give a toast, but refuses, and the crowd turns to Alfredo, who agrees to sing a brindisi – a drinking song (Alfredo, Violetta, chorus: Libiamo ne' lieti calici – "Let's drink from the joyful cups")...