Udayapur is a district located in the Koshi Province of Nepal. It is situated in the eastern part of the country and covers an area of 2,063 square kilometers. The district is named after Udayapur, a historic town located in the southern part of the district.

Udayapur district is bordered by Bhojpur and Khotang districts to the north, Okhaldhunga and Solukhumbu districts to the west, Saptari and Siraha districts to the south, and Sunsari district to the east.

The district has a diverse topography, ranging from the foothills of the Himalayas in the north to the flat plains of the Terai in the south. The district is known for its natural beauty, including dense forests, hills, rivers, and waterfalls.

Udayapur is home to a variety of ethnic groups, including Rai, Limbu, Magar, Tamang, and Brahmin. The main languages spoken in the district are Nepali, Rai, and Limbu.

Some of the major attractions in Udayapur district include the Koshi Tappu Wildlife Reserve, the Udayapur Hill, the Raighat Hydroelectric Dam, and the Chaudandigadhi Fort. The district is also known for its traditional handicrafts, such as bamboo and cane products.