Madhesh Province (Nepali: मधेश प्रदेश) is a province in the southeastern region of Nepal that was formed after the adoption of the Constitution of Nepal. It is Nepal's most populous province, and smallest province by area. It borders Province No. 1 to the east, Bagmati Province to the north, and India’s Bihar state to the south. It has an area of 9,661 km2 (3,730 sq mi)-about 6.5% of the country's total area. It has a population of 6,126,288 as per the 2021 Nepal census, making it the most populated province of Nepal. The Koshi River and Koshi Tappu Wildlife Reserve acts as provincial demarcation border between Madhesh Province and Province No.1 in the east. And the demarcation line between Chitwan National Park and Parsa National Park (previously Wildlife Reserve) acts as provincial demarcation border between Madhesh Province and Bagmati Province in the west. The province includes eight districts from Saptari District in the east to Parsa District in the west. The majority of the province's population speaks Maithili, Bhojpuri and Nepali and Bajjika.