Neurotrophin-3, or NT-3, is a neurotrophic factor, in the NGF-family of neurotrophins. It is a protein growth factor that has activity on certain neurons of the peripheral and central nervous system; it helps to support the survival and differentiation of existing neurons, and encourages the growth and differentiation of new neurons and synapses. NT-3 is the third neurotrophic factor to be characterized, after NGF and BDNF.
NT-3 is unique among the neurotrophins in the number of neurons it has potential to stimulate, given its ability to activate two of the receptor tyrosine kinase neurotrophin receptors (TrkC and TrkB). Mice born without the ability to make NT-3  have loss of proprioceptive and subsets of mechanoreceptive sensory neurons.