Arrah is a city and a municipal corporation in Bhojpur district in the state of Bihar, India. The name is also sometimes transliterated as Ara. It is the district headquarters of Bhojpur district, located near the confluence of the Ganges and Sone rivers, some 24 miles from Danapur and 36 miles from Patna.

During the Indian rebellion of 1857, a small party of British officers and Indian soldiers was besieged in the Little House at Arrah, by a band of armed soldiers under the command of 80-year-old Veer Kunwar Singh, the Zamindar of adjacent Jagdishpur. They withstood the siege for three weeks until relieved by other East India Company troops.

As per 2011 census, Arrah Municipal Corporation had a total population of 261,099, out of which 139,319 were males and 121,780 were females. It had a sex ratio of 874. The population below 5 years was 34,419. The literacy rate of the 7+ population was 83.41 per cent.

As of 2001 India census, Arrah had a population of 203,395. Males constitute 54% of the population and females 46%. Arrah has an average literacy rate of 67%, higher than the national average of 59.5%; with 60% of the males and 40% of females literate.

Climate is characterized by relatively high temperatures and evenly distributed precipitation throughout the year. The Köppen Climate Classification sub-type for this climate is “Cfa” (Humid Subtropical Climate).