A megaphone is a cone-shaped device designed to amplify sound.

They are often used at some sporting events, protests, rallies and crowd control. Their benefits are that they do not require a sound system, or a microphone, and the device is hand-held and portable.

In Wagner's opera Siegfried, the voice of the dragon Fafnir was to be sung by a bass, offstage rear, using an acoustic megaphone.

Most megaphones used today are electronic, with a small battery powered amplifier. This type of megaphone is also referred to as a bullhorn or loudhailer.