Masterbatch (MB) is a solid additive for plastic used for coloring plastics (color masterbatch) or imparting other properties to plastics (additive masterbatch). A liquid dosage form is called liquid color. Masterbatch is a concentrated mixture of pigments and/or additives encapsulated during a heat process into a carrier resin which is then cooled and cut into a granular shape. Masterbatch allows the processor to colour raw polymer economically during the plastics manufacturing process.

The alternatives to using masterbatches are buying a fully compounded material (which may be more expensive and less open to e.g. color variability of the product), or compounding from raw materials on site (which is prone to issues with achieving full dispersion of the colorants and additives, and prone to preparing more material than what is used for the production run). In comparison with pure pigments, masterbatches require more storage space and their lead times are longer. Another disadvantage is additional exposure of heat (“heat history”) to both the carrier and the additive; this may be important e.g. for marginally thermally stable pigments