Glia, the non-neuronal cells in the nervous systems, are both passive and active participants in diverse arrays of neuronal function. The diversity of glial cells in various animal species appears to be correlated with the complexity of brains. In the animal Drosophila melanogaster, glia are similarly categorized to their mammalian counterparts in morphology and function. Surface glia cover the outermost surface of the brain and function as a blood-brain-barrier to protect the nervous system. Cortex glia, similar to mammalian astrocytes, enwrap around the neuronal cell bodies and provide trophic support. Neuropil glia, similar to mammalian astrocytes and oligodendrocytes, are closely associated with the synapse-enriched neuropils and regulate synapse formation, synaptic function, and underlie the mechanism of circuit and behavior. This short monograph focuses on Drosophila glia, discusses the classification of different glial subtypes and their developmental origins, and provides an overview of different glial-mediated activity crucial for the development and function of the nervous system. This context serves as a general introduction to the molecular and cellular basis of glial function in normal and pathological brains.