A metronome (from Ancient Greek μέτρον (métron) 'measure', and νομός (nomós) 'custom, melody') is a device that produces an audible click or other sound at a regular interval that can be set by the user, typically in beats per minute (BPM). Metronomes may include synchronized visual motion. Musicians use the device to practise playing to a regular pulse.

A kind of metronome was among the inventions of Andalusian polymath Abbas ibn Firnas (810–887). In 1815, German inventor Johann Maelzel patented his mechanical, wind-up metronome as a tool for musicians, under the title "Instrument/Machine for the Improvement of all Musical Performance, called Metronome". In the 20th century, electronic metronomes and software metronomes were invented.

Musicians practise with metronomes to improve their timing, especially the ability to stick to a regular tempo. Metronome practice helps internalize a clear sense of timing and tempo. Composers and conductors often use a metronome as a standard tempo reference—and may play, sing, or conduct to the metronome. The metronome is used by composers to derive beats per minute if they want to indicate that in a composition. Conductors use a metronome to note their preferred tempo in each section.

When interpreting emotion and other qualities in music, performers seldom play exactly on every beat; expressive, flexible rubato may be used at times. Typically, every beat of a musically expressive performance does not align exactly with each click of a metronome. This has led some musicians to criticize use of a metronome, because metronome time is different from musical time.