Neuropeptides are small protein-like molecules used by neurons to communicate with each other. They are neuronal signaling molecules. The brain largely functions by virtue of neuropeptides.

Neuropeptides are expressed and released by neurons, and mediate or modulate neuronal communication by acting on cell surface receptors. The human genome contains about 90 genes that encode precursors of neuropeptides. Neuropeptides can be clustered in at least 10 subfamilies according to structural feature

The Neuropeptide Database is the internet resource to data about all known neuropeptides, their genes, precursors and expression in the brain.