In vertebrate anatomy, a ganglion is a tissue mass that contains the dendrites and central bodies (or "somas") of nerve cellss, in most case ones belonging to the peripheral nervous system . Within the central nervous system such a mass is often called a nucleus. An interconnected group of ganglia is called a plexus.

There are two major groups of ganglia: spinal ganglia and autonomic ganglia. The former contains the cell bodies of sensory nerves and the latter contains the cell bodies of autonomic nerves.

See also: nervous system, neuron, Ganglion cyst