A nickel-metal hydride battery, abbreviated NiMH or Ni-MH, is a type of rechargeable battery. It is very similar to the nickel-cadmium cell (NiCd). NiMH use positive electrodes of nickel oxyhydroxide (NiOOH), like the NiCd, but the negative electrodes use a hydrogen-absorbing alloy instead of cadmium. A NiMH battery can have two to three times the capacity of an equivalent size NiCd, and their energy density approaches that of a lithium-ion cell.

The typical specific energy for small NiMH cells is about 100 W@h/kg, and for larger NiMH cells about 75 W@h/kg (270 kJ/kg). This is significantly better than the typical 40-60 W@h/kg for Ni-CD, and similar to the 100-160 W@h/kg for Li-ion. NiMH has a volumetric energy density of about 300 W@h/L (1080 MJ/m³ ), significantly better than nickel-cadmium at 50-150 W@h/L, and about the same as Li-ion at 250-360 W@h/L.

NiMH batteries normally operate at 1.2 V per cell, somewhat lower than conventional 1.5 V cells, but will operate most devices designed for that voltage. about 22% of portable rechargeable batteries sold in Japan in 2010 were NiMH. In Switzerland in 2009, the equivalent statistic was approximately 60%. This percentage has fallen over time due to the increase in manufacture of Li-ion batteries: In 2000, almost half of all portable rechargeable batteries sold in Japan were NiMH.

Apllication:
All-electric plug-in vehicles such as the General Motors EV1, Honda EV Plus, Ford Ranger EV and Vectrix scooter.
Hybrid vehicles such as the Toyota Prius, Honda Insight, Ford Escape Hybrid, Chevrolet Malibu Hybrid, and Honda Civic Hybrid also use them.

NiMH technology is used extensively in automatic guided vehicles(AGV) and solar panels.