In music composition, fragmentation is the use of fragments or the "division of a musical idea (gesture, motive, theme, etc.) into segments". It is used in tonal and atonal music, and is a common method of localized development and closure.

Fragmentation is related to Arnold Schoenberg's concept of liquidation, a common compositional technique that describes the reduction of a large-scale musical idea to its essential form (such as a contour line, a specific harmonic motion, or the like). Liquidation shapes much thematically-driven music, such as that by Béla Bartók, Stravinsky, and Schoenberg himself. It is important to understand that, although they are related, fragmentation and liquidation are separate processes and concepts.