The bass guitar (also called electric bass, or simply bass; pron.: /ˈbeɪs/) is a stringed instrument played primarily with the fingers or thumb, by plucking, slapping, popping, tapping, thumping, or picking.

The bass guitar is similar in appearance and construction to an electric guitar, but with a longer neck and scale length, and four, five, six, or eight strings. The four-string bass—by far the most common—is usually tuned the same as the double bass, which corresponds to pitches one octave lower than the four lower strings of a guitar (E, A, D, and G). The bass guitar is a transposing instrument, as it is notated in bass clef an octave higher than it sounds (as is the double bass) to avoid excessive ledger lines. Like the electric guitar, the bass guitar is plugged into an amplifier and speaker for live performances.