Monaural or monophonic sound reproduction (often shortened to mono) is single-channel. Typically there is only one microphone, one loudspeaker, or (in the case of headphones and multiple loudspeakers) channels are fed from a common signal path. In the case of multiple microphones the paths are mixed into a single signal path at some stage.

Monaural sound has been replaced by stereo sound in most entertainment applications. However, it remains the standard for radiotelephone communications, telephone networks, and Audio induction loops for use with hearing aids. A few FM radio stations, particularly of the talk radio variety, choose to broadcast in monaural sound, as a monaural signal has a slight advantage in signal strength over a stereophonic signal of the same power.

While some experiments were made with stereophonic recording and reproduction from the early days of the phonograph in the late 19th century, until the second half of the 20th century monaural was the rule for almost all audio recording.