Astrocytes are cells located in the human brain and spinal cord. They are the most abundant cells in the human brain. Shaped like stars, they provide many essential brain functions, such as holding neurons in place, getting nutrients to neurons and nervous tissue, disposal of dead neurons, maintaining the blood-brain barrier, and repairing and scarring the brain and spinal cord following traumatic injury. They are responsible for astrocytomas, or brain tumors that develop from astrocytes. This condition can occur in the brain and spinal cord, at any age, and primarily in males.

Studying astrocytes plays a huge role in neuroscience since astrocytes communicate with neurons. It is suggested that astrocytes regulate neural stem cells and may play a role in depression.