Cochlear implants have been successful in restoring partial hearing to profoundly deaf people. The success of cochlear implants can be attributed to the combined efforts of scientists from various disciplines, including bioengineering, physiology, otolaryngology, speech science, and signal processing. Each of these disciplines contributed to various aspects of the cochlear implant design. Signal processing, in particular, played an important role in the development of different techniques for deriving electrical stimuli from the speech signal. The purpose of this article is to present a review of various signal-processing techniques that have been used for cochlear prosthesis over the past 25 years.