Rock and roll (often written as rock & roll, rock-n-roll, rock 'n' roll, rock n' roll or Rock n' Roll) is a genre of popular music that evolved in the United States during the late 1940s and early 1950s. It originated from African American music such as jazz, rhythm and blues, boogie-woogie, electric blues, gospel, and jump blues, as well as country music. While rock and roll's formative elements can be heard in blues records from the 1920s and in country records of the 1930s, the genre did not acquire its name until 1954.

According to the journalist Greg Kot, "rock and roll" refers to a style of popular music originating in the United States in the 1950s. By the mid-1960s, rock and roll had developed into "the more encompassing international style known as rock music, though the latter also continued to be known in many circles as rock and roll." For the purpose of differentiation, this article deals with the first definition.

In the earliest rock and roll styles, either the piano or saxophone was typically the lead instrument. These instruments were generally replaced or supplemented by the electric guitar in the mid-to-late 1950s. The beat is essentially a dance rhythm with an accentuated backbeat, almost always provided by a snare drum. Classic rock and roll is usually played with one or more electric guitars (one lead, one rhythm) and a double bass (string bass). After the mid-1950s, electric bass guitars ("Fender bass") and drum kits became popular in classic rock.