A medley is a term used in music to describe a piece composed from parts of existing pieces played one after another, sometimes overlapping). Medleys are common in popular music, and most medleys are songs rather than instrumentals. A medley which is a remixed series is called a megamix, often done with tracks for a single artist, or for popular songs from a given year or genre. A cover version combining elements of multiple pre-existing songs is a cover medley).

In addition to music, the term medley can also refer to a mixture of heterogeneous elements, a hodgepodge, or a jumble. For example, a medley of desserts could refer to a diverse assortment of desserts, while a medley of sounds could refer to a mixture of different noises.

In swimming, a medley is a race in which swimmers use a different stroke for each section of the race, either individually or in teams. The 4x100 meters medley is a relay race in which each swimmer swims one of the four strokes (backstroke, breaststroke, butterfly, and freestyle) .

In musical theater productions, medleys are often seen in overtures that play at the beginning of the show. A piece of music with Medley Form is one of constant variation, starting off with one idea and then moving on to another, never to come back to the first idea. Examples of medleys include musicians playing ‘mashups’ or combinations of other songs.