Hindi is the official language of the state of Bihar, as per the Bihar Official Language Act, 1981.

Hindi is spoken by the largest number of people in Bihar, followed by Maithili, Bhojpuri, and Urdu.

Maithili is spoken in the Mithila region of Bihar, which includes the districts of Madhubani, Darbhanga, Samastipur, and Begusarai.

Bhojpuri is spoken in the Bhojpur region of Bihar, which includes the districts of Bhojpur, Buxar, and Kaimur.

Hindi is spoken in the Magadh region of Bihar, which includes the districts of Patna, Gaya, and Nalanda.

Urdu is spoken in the Seemanchal region of Bihar, which includes the districts of Kishanganj, Araria, and Purnia.

Angika is spoken in the Angika region of Bihar, which includes the districts of Bhagalpur, Munger, and Jamui.

Vajjika is spoken in the Vajjika region of Bihar, which includes the districts of Vaishali, Muzaffarpur, and Sitamarhi.

Magahi is spoken in the Magahi region of Bihar, which includes the districts of Patna, Gaya, and Nalanda.

Khortha is spoken in the Khortha region of Bihar, which includes the districts of Rohtas and Kaimur.

Surjapuri is spoken in the Surjapuri region of Bihar, which includes the districts of Saran and Siwan.

Braj is spoken in the Braj region of Bihar, which includes the districts of Bhojpur and Buxar.

Awadhi is spoken in the Awadhi region of Bihar, which includes the districts of West Champaran and East Champaran.

Haryanvi is spoken in the Haryanvi region of Bihar, which includes the district of Kishanganj.

Rajasthani is spoken in the Rajasthani region of Bihar, which includes the district of Kishanganj.