Granulocytes are a category of white blood cells, characterised by the fact that all types have differently staining granules in their cytoplasm on light microscopy. They are also being referred to as polymorphnuclear leukocytes (PMN or PML), because of the varying shapes of the nucleus, which is usually lobed into three segments.

The most abundant granulocyte is the neutrophil (neutrally staining granules). Often, the words "granulocyte" and "neutrophil", as well as other related terms (such as granulocytosis), are used interchangeably.

The granulocytes are:

• Neutrophil granulocytes
• Eosinophil granulocytes
• Basophil granulocytes

See also: white blood cell, blood count