Which language is Nepal's official language?

The official language of Nepal is Nepali, which is also known as Gorkhali.12

Nepali belongs to the Indo-Aryan branch of the Indo-European language family and is primarily spoken in the Tarai and mid-mountain regions of the country. While Nepali serves as the official language, the nation is home to a diverse array of other languages, particularly those from the Tibeto-Burman family, such as Newari, Tamang, Gurung, Magar, and Sherpa.23