The play begins in the flat of wealthy Algernon Moncrieff (Algy) in London's fashionable West End. Algernon's aunt (Lady Bracknell) and her daughter (Gwendolen Fairfax) are coming for a visit, but Mr. Jack Worthing (a friend of Algy's) arrives first. Algernon finds it curious that Jack has announced himself as "Ernest." When Jack explains that he plans to propose marriage to Gwendolen, Algy demands to know why Jack has a cigarette case with the inscription, "From little Cecily with her fondest love." Jack explains that his real name is Jack Worthing, squire, in the country, but he assumes the name "Ernest" when he ventures to the city for fun. Cecily is his ward. While devouring all the cucumber sandwiches, Algernon confesses that he, too, employs deception when it's convenient. He visits an imaginary invalid friend named Bunbury when he needs an excuse to leave the city.
Lady Bracknell and Gwendolen arrive. Algernon explains that he cannot attend Lady Bracknell's reception because he must visit his invalid friend, Bunbury, but he offers to arrange the music for her party. While Algernon distracts Lady Bracknell in another room, Jack proposes to Gwendolen. Unfortunately, she explains that she really wants to marry someone named Ernest because it sounds so solidly aristocratic. However, she accepts his proposal, and he makes a mental note to be rechristened Ernest. Lady Bracknell returns and refutes the engagement. She interrogates Jack and finds him lacking in social status. On her way out, Lady Bracknell tells Jack that he must find some acceptable parents. Gwendolen returns for Jack's address in the country. Algernon overhears and writes the address on his shirt cuff. He is curious about Cecily and decides to go "bunburying" in the country.
