Religion is an integral part of the history of a civilization. Bihar as history tells has seen many great civilizations on its soil and also produced some greatest persons of their time. In ancient times it was Bihar where Buddhism and Jainaism took their birth. According to the census data of 2001 Bihar's religious communities are a combination of Hindus, Muslims, Christians, Sikhs, Buddshist, Jaina and Jews. The exact data of 2001 Census says 83% of total populations are Hindus while 17% practised Islam. In Bihar religion is a way of life. Every aspect of life is closely attached to religion. Several festivals are celebrated in the State having associated with different. Every festival be it Chhath or Holi or Depawali or Maharam or Id or X-mas celebrated with full glamour and enthusiasm. Strong bond of fraternity and brotherhood can be seen during observance of various festivals in the state.
Hinduism is a major religion in Bihar. Most of the people follow this religion. The common people are so religious that it becomes a part of their every day life. There are several Hindu temples throughout the state. Many temple sites are also famous pilgrimage sites like Gupteswar Dham, Deo Markandeya, Bhaluni Temple and Chaurasan Mandir. Besides shrines in the temple one can see local deities are worshipped in some roadside places or beneath a tree. Several Hindu festivals having religious connotation are observed in the state like Durga Puja, Chhath puja, Dusserah, Holi, Deepavali, Bhaiya Dooj and Saraswati Puja. As most of the Hindus believe in polytheism there are variations within the Hindu religion which resulted into various cults like Shakta, Shaiva and Vaishnavas. All these cults have their presence in Bihar. Besides this there are regional variation in observance of different religious rituals in Mithila and Bhojpuri speaking region of Bihar.
Islam is the second largest religion in Bihar consisting 17% of the total population. There are numerous mosques within the state some of them are of mediaeval time. Bihar used to be a main centre of Sufism in mediaeval time frequently visited by many Sufi saints. Several Muslim festivals like Id-ul-Juha, Ramazan, and Maharam are celebrated throughout the state with traditional flavor. Christians also has a sizeable population in the state. There are several churches in the state Patna being the most important. Bihar is the birth place of Sikhism. Guru Gobind Singh the tenth and last of Sikh guru was born in Patna. The Harmandir Takht or Patna Sahib commemorates Guru Gobind Singh and is a sacred place of Sikh pilgrimage. The site where the Guru was born is marked by a temple containing his cradle and shoes.
Bihar was the birth place of Buddhism. A lot of place in Bihar is related to the life and teachings of Buddha and become sacred places for Buddhist. They are Gaya, Aurangabad, Nalanda and Patna. Bihar was also the same fertile ground where Jainaism emerged. Pawapuri is a holy place of Jaina religion where Mahavira breathed his last. Besides all these religion tribals of Bihar have their own religion which is very different from region to region and from tribe to tribe. In addition to gods and goddesses they believe in demons and spirits and worship many supernatural beings. Every tribal village has a sacred grove called Jaher or sarma where the village priest performs all worship on behalf of the whole village.