A kinocilium is a special type of cilium on the apex of hair cells located in the sensory epithelium of the vertebrate inner ear.

[1] Together with stereocilia, the kinocilium regulates depolarization and hyperpolarization of the hair cell, which is a neuron that can generate action potentials.

[citation needed] Kinocilia are present in the crista ampullaris of the semicircular ducts and the sensory maculae of the utricle and saccule.

The depolarization of the hair cell causes neurotransmitter to be released and an increase in firing frequency of cranial nerve VIII.

[3] The apical surface of a sensory fish hair cell usually has numerous stereocilia and a single, much longer kinocilium.

Deflection of the stereocilia toward or away from the kinocilium causes an increase or decrease in the firing rate of the sensory neuron innervating the hair cell at its basal surface.