Bihar Diwas or Bihar Diwas or Bihar Day is observed every year on March 22, marking the formation of the state of Bihar. It was on this day when the British carved out the state from Bengal Presidency in 1912. The Day is a public Holiday in Bihar. Bihar Divas was started and celebrated on large scale by Bihar Government in the tenure of Nitish Kumar. Apart from India, it is celebrated in countries including United States, Britain, Australia, Canada, Bahrain, Qatar, United Arab Emirates, Trinidad and Tobago and Mauritius.

Some people argue that Bihar came into existence on April 1, 1912 and not on March 22. However, Bihar Government observes Bihar Diwas on March 22