A three-chord song is a song whose music is built around three chords that are played in a certain sequence. A common type of three-chord song is the simple twelve-bar blues used in blues and rock and roll.

Typically, the three chords used are the chords on the tonic, subdominant, and dominant (scale degrees I, IV and V): in the key of C, these would be the C, F and G chords. Sometimes the V⁷ chord is used instead of V, for greater tension.

The I (tonic), IV (subdominant) and V (dominant) chords (primary triads) together encompass all seven tones of the tonic's major scale. These three chords are a simple means of covering many melodies without the use of passing notes.

The order of the chord progression may be varied; popular chord progression variations using the I, IV and V chords of a scale are:

• V – I – IV
• I – V – IV – V
• V – IV – I

Beside the I, IV and V chord progression, other widely used 3-chord progressions are:^[1]

• I – vi – V
• I – ii – V

Songwriter Harlan Howard once said "country music is three chords and the truth."^[2]

Lou Reed said "One chord is fine. Two chords is pushing it. Three chords and you're into jazz."^[3] Reed nevertheless wrote many songs with unique or complex chord progressions himself, such as the material on Berlin.

• Cadence (music)
• I–V–vi–IV progression
• Twelve-bar blues
• Bergamask