A nickel-metal hydride battery, abbreviated NiMH, is a type of rechargeable battery similar to a nickel-cadmium (NiCd) battery but using a hydrogen-absorbing alloy for the negative electrode instead of cadmium. As in NiCd batteries, the positive electrode is nickel oxyhydroxide (NiOOH). A NiMH battery can have two to three times the capacity of an equivalent size NiCd. However, compared to the lithium-ion battery, the volumetric energy density is lower and self-discharge is higher.

Common AA batteries (penlight-size) have nominal charge capacities (C) ranging from 1100 mA·h to 2700 mA·h at 1.2 V, usually measured at a discharge rate of 0.2×C per hour. Useful discharge capacity is a decreasing function of the discharge rate, but up to a rate of around 1×C (full discharge in one hour), it does not differ significantly from the nominal capacity.

Applications of NiMH type batteries includes all-electric plug-in vehicles such as the Toyota RAV4 EV, General Motors EV1, Honda EV Plus, and Ford Ranger EV. Hybrid vehicles such as the Toyota Prius, Honda Insight, and Honda Civic Hybrid also use them. NiMH technology is used extensively in rechargeable batteries for consumer electronics, and it will also be used on the Alstom Citadis low floor tram ordered for Nice, France; as well as the humanoid prototype robot ASIMO designed by Honda.

NiMH batteries are commonly considered less detrimental to overall environmental health than NiCd batteries due to absence of toxic cadmium. The overall environmental impact of mining the various alternate metals that form the negative electrode may be more or less than cadmium, depending on the metal.