Fifths tuning is a non-standard tuning for the double bass, used primarily in classical and jazz music. In this tuning, the double bass is tuned like a cello but an octave lower (C-G-D-A low to high).

Although fifths tuning was once the most common double bass tuning in France in the 19th century,^[1] standard fourths tuning (E-A-D-G) has since become the most used tuning for the instrument. Fifths has recently been repopularised by a small number of bassists, most notably American Red Mitchell and Canadian Joel Quarrington.

Its advocates^{[citation needed]} say the advantages of fifths tuning are:

• Increased resonance, volume and quality of sound (the strings have more common overtones, causing the strings to vibrate sympathetically).
• Superior intonation with the rest of the string section due to the uniform tuning (for classical players).
• Best method of obtaining a low C, without an extension or a fifth string.
• Mostly used by jazz players for the major tenth which can be played easily without a position shift.

• Double bass
• Joel Quarrington
• Red Mitchell
• Circle of fifths