A cochlear implant (CI) is a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf or severely hard of hearing. The cochlear implant is often referred to as a bionic ear.

As of December 2010, approximately 219,000 people worldwide have received cochlear implants; in the United States, roughly 42,600 adults and 28,400 children are recipients. The vast majority are in developed countries due to the high cost of the device, surgery and post-implantation therapy. A small but growing segment of recipients have bilateral implants (one implant in each cochlea).

Cochlear implants can restore hearing in patients suffering deafness due to loss of sensory hair cells in their cochlea. In those patients, they can often restore sufficient hearing to allow unaided understanding of speech in a quiet background, but the restored, electrical hearing is much less rich than natural hearing, and offers only very limited appreciation of musical melody, or speech understanding in noisy environments.