Bill is a song heard in Act II of Kern and Hammerstein's classic 1927 musical Show Boat. The song was written for Kern and P.G. Wodehouse's 1917 musical Oh Lady, Lady! for Vivienne Segal to perform, but withdrawn because it was considered too melancholy for that show. However, when Kern and Hammerstein were at work on the serious and somewhat tragic Show Boat, they decided that the song would be perfect for a nightclub scene in the show. Hammerstein revised Wodehouse's original lyrics somewhat (though he would always give full credit to Wodehouse for the song and take none for himself), and the song was given to real-life nightclub singer Helen Morgan, who portrayed the mulatto Julie in Show Boat, to sing.

The song is sung only once in the show and is highly emotional, with the singer supposedly on the verge of tears. It is sung in an audition scene in Act II. At the Trocadero, a local Chicago night club, Julie LaVerne, the former leading lady of the show boat, is the featured singer. Julie, who is of mixed blood, has been permanently abandoned by her white husband, Steve Baker, years after the two were forced to leave the show boat because of their interracial, and illegal, marriage. Despondent, Julie has taken to drink and is quickly becoming an alcoholic. At the urging of Jim Green, the nightclub manager, Julie rehearses the song "Bill", which is a woman's confession of deep love for a less-than-perfect man named Bill, and it is clear that the emotion that Julie puts into the song comes from the fact that she is really thinking about her husband as she sings.

"Bill" became one of Helen Morgan's signature songs, and onstage she sang it in her trademark style sitting atop a piano. Although the song is sung only once in Show Boat and never reprised, it has become one of the musical's most famous songs.

On film, Helen Morgan sang Bill both in the prologue to the 1929 part-talkie film version of "Show Boat" and in the classic 1936 film version. Lena Horne was filmed singing it for the Jerome Kern biopic Till the Clouds Roll By, but the scene was eventually cut, and Ava Gardner, using the dubbed-in voice of Annette Warren, sang it in the 1951 Technicolor remake of "Show Boat".