None (its a misconception that Hindi is a national language which is the mother language of ~40% population)
Official languages (not national language) of the Union Government of Republic of India is English as mentioned in article 343/1 of the Constitution of India. Currently there are 22 official languages in India Assamese, Bengali, Bodo, Dogri, Gujarati, Hindi, Kannada, Kashmiri, Konkani, Maithili, Malayalam, Meitei (Manipuri), Marathi, Nepali, Odia, Punjabi, Sanskrit, Santali, Sindhi, Tamil, Telugu, Urdu. States of India were free to adopt one or more local languages for all or any of the official purposes of that state. All 22 languages carry equal official status and Government documents can be in any of the 22 recognized official languages.
