Bihar (; Hindi pronunciation: [bɪˈɦaːr] (listen)) jiha ce a gabashin Indiya. Duk da haka, ita ce jiha ta goma sha uku mafi girma a Indiya, tare da yanki na 94,163 km2 (36,357 sq mi). Jihar ta uku mafi girma ta yawan jama'a, tana da alaƙa da Uttar Pradesh zuwa yamma, Nepal zuwa arewa, arewacin West Bengal zuwa gabas, tare da Jharkhand zuwa kudu. Bihar Plain ya rabu da kogin Ganges, wanda ke gudana daga yamma zuwa gabas.
na uku mafi girma a jihar ta yawan jama'a