At Buckingham Palace in London, England, the British royal family waits out a rainstorm before having their photograph taken on the palace lawn. However, puddles of water cause the photographer’s electrical cables to short circuit, and every member of the House of Wyndham is electrocuted. In wake of the tragedy, Parliament consults genealogical records, searching for a rightful successor. They learn of a liaison between an American woman and a British duke, which resulted in the birth of a son. Though now deceased, that man is survived by a son, Ralph Jones, an American lounge singer. Two British officials travel to Las Vegas, Nevada, to inform the uncouth musician that he is the new King of England. On arriving in London, Ralph meets Sir Cedric Willingham, the royal secretary. Willingham is dismayed at Ralph’s casual attire and flippant attitude, but takes it upon himself to instruct the American in appropriate royal protocol. In the picture gallery, Ralph admires his grandfather’s portrait, while Willingham recapitulates several hundred years of British history. At the end of the day, Ralph retires to his sumptuous bedroom apartment, impressed by the imperial crown placed next to his bed. Willingham wryly advises Ralph to practice wearing the weighty headpiece. The next morning, Sir Willingham meets with the Prime Minister and Lord Percival Graves at 10 Downing Street. Graves, disgusted at the thought of an American sovereign, suggests reinstating the House of Stewart’s claim to the throne. Willingham notes that such an act would position Percival Graves to be king. Meanwhile, Ralph leaves Buckingham Palace and visits a strip club, where he falls head over heels in love with a stripper who is too shy to complete her striptease. After the show, Ralph goes backstage to meet the embarrassed woman, whose name is Miranda. He introduces himself as the King of England, and asks her out on a date, but Miranda thinks he is joking. The next morning, Miranda sees a television news report about Ralph’s royal lineage, but before she can learn more, Lord Graves knocks on her door. Having learned of Miranda’s encounter with Ralph, he pressures her to have an affair with the new king, certain that the resulting scandal would force Ralph to abdicate the throne. Miranda recognizes Graves’s ploy, but she cannot turn down the extraordinary amount of money he offers. Meanwhile, Ralph meets the Prime Minister, who makes a long-winded speech about hosting a reception for the King of Zambezi, Africa. When Ralph falls asleep, the Prime Minister expresses dismay at the thought of introducing an African dignitary to the imbecile king. Later, Willingham curtails Ralph’s plans to go out with Miranda, but the king insists, and Miranda is allowed to come to Buckingham Palace for dinner. The next day, Willingham cautions Ralph about getting romantically involved with a commoner, but the king protests they are just friends. The secretary agrees to let the friendship continue, so long as the couple does not go out in public. A few days later, photographers take pictures of Miranda as she leaves the palace, and Willingham advises Ralph to stop seeing her. That afternoon, Ralph prepares to meet King Mulambon of Zambezi. He falters while delivering his welcome speech, and invites the African king to play a game of darts at the local pub. Mulambon enjoys Ralph’s carefree attitude, and the diplomatic visit is declared a success. Although public opinion of the new king soars, Ralph confesses to Willingham that the royal job is a lonely one. One night, Ralph sneaks out of the palace and invites Miranda to meet him. Lord Graves sends a photographer after the couple, and Ralph unwittingly poses for the picture, his arm wrapped around his girl friend. Miranda thwarts the photographer and leads Ralph to a park gazebo, where they kiss. Sometime later, Willingham and the king retreat to Windsor Castle with the Prime Minister, who discusses the importance of a political alliance with Finland, which has recently discovered untapped oil resources. The British officials inform Ralph that he will meet Finland’s Princess Anna and take steps toward marrying her. Indignant at being treated like a puppet, Ralph “quits” being king. Willingham challenges Ralph to consider the greater good, and Ralph agrees to host a ball in the Princess’s honor. On the day of the Finnish royal visit, Lord Graves deceives Miranda into thinking Ralph has invited her to the ball. Meanwhile, Ralph meets Princess Anna and is impressed by her beauty. However, he soon realizes they have nothing in common. At the ball, they go out on the balcony to talk, and Anna shocks the king with a sexual proposition. Ralph decides to liven the party by performing a rousing rendition of a rock and roll song on the harpsichord. Midway through his act, he notices Miranda among the guests and invites her to dance. Just then, the King of Finland receives an envelope containing photographs of Ralph and Miranda kissing in the gazebo. At the end of the song, Princess Anna demands to know about Ralph’s relationship to Miranda. Tongue-tied, Ralph cannot offer an explanation, causing Miranda and the royal guests to leave. The next day, the media ridicules the new king, and Lord Graves urges Parliament to oust the American. Determined to make amends, Ralph finds Miranda at her mother’s house. There, she confesses that Lord Graves bribed her to put Ralph in compromising situations. An angry Ralph returns to Buckingham Palace and confronts Willingham about the true story behind his ascent to the throne. Willingham confesses that he, too, is the result of an illegitimate affair between a royal and a commoner, and nearly equal to Ralph in terms of succession. However, he had no interest in being king. Ralph thanks the secretary for his honesty. At Parliament the next day, King Ralph apologizes for his recent gaffes, before renouncing his title as King of England to Sir Cedric Willingham. Having finally won England’s approval, Ralph locates Miranda and asks if they can start over. She leaps into his arms. Sometime later, King Cedric awards Ralph a dukedom. Ralph forms a band, “The Dukettes,” and lives happily ever after with Miranda and their son, Ralph II.