A constitution is the aggregate of fundamental principles or established precedents that constitute the legal basis of a polity, organization or other type of entity, and commonly determines how that entity is to be governed. Constitution Day is celebrated on Asoj 3 every year in recognition of the contribution of the constitution by the Constituent Assembly in the year 2015 (2072 B.S.).

The Constitution of Nepal was promulgated on 16 September 2015. It entered into force on 20 September 2015, replacing the Interim Constitution of 2007.

On the main day of the Constitution Day celebrations, it has been decided to hoist the national flag at public media and at the homes of common citizens, as well as to celebrate Dipawali in the evening.The Constitution of Nepal is divided into 35 parts, 308 articles, and 9 schedules.Part 3 of the Constitution of Nepal describes the fundamental rights and duties of Nepalese citizens.

Article 16 to Article 46 of the Nepalese Constitution guarantees 31 fundamental rights to Nepalese people. These include the freedom to live with dignity, freedom of speech and expression, religious and cultural freedom, right against untouchability and discrimination, etc. Article 48 describes the duties of every Nepalese. It emphasizes safeguarding the nationality, sovereignty, and integrity of Nepal.

The constitution was drafted by the Second Constituent Assembly following the failure of the First Constituent Assembly to produce a constitution in its mandated period after the devastating earthquake in April 2015. The constitution was endorsed by 90% of the total legislators.