21 February was declared to be the International Mother Language Day by UNESCO in 1999. It has been observed throughout the world since 21 February 2000. The declaration came up in tribute to the Language Movement done by the Bangladeshis (then the East Pakistanis).

When Pakistan was created in 1947, it had two geographically separate parts: East Pakistan (currently known as Bangladesh) and West Pakistan (currently known as Pakistan). The two parts were very different to each other in the sense of culture and language. The two parts were also separated by India in between.

In 1948, the then Government of Pakistan declared Urdu to be the sole national language of Pakistan, even though Bengali or Bangla was spoken by the majority of people combining East Pakistan and West Pakistan. The East Pakistan people protested, since the majority of the population was from East Pakistan and their mother language was Bangla. They demanded Bangla to be at least one of the national languages, in addition to Urdu. The demand was raised first by Dhirendranath Datta from East Pakistan on 23 February 1948, in the constituent Assembly of Pakistan.

To demolish the protest, the government of Pakistan outlawed public meeting and rallies. The students of the University of Dhaka, with the support of the general public, arranged massive rallies and meetings. On 21 February 1952, police opened fire on rallies. Abdus Salam, Abul Barkat, Rafiq Uddin Ahmed, Abdul Jabbar and Shafiur Rahman died, with hundreds of others injured. This was a rare incident in history, where people sacrificed their lives for their mother tongue.[citation needed]

Since then, Bangladeshis celebrate the International Mother Language Day as one of their tragic days. They visit the Shaheed Minar, a monument built in memory of the martyrs and its replicas to express their deep sorrow, respect and gratefulness to them.[citation needed]

International Mother Language Day is a national holiday in Bangladesh. The resolution was suggested by Rafiqul Islam and Abdus Salam, Bengalis living in Vancouver, Canada. They wrote a letter to Kofi Annan on 9 January 1998 asking him to take a step for saving the world's languages from extinction by declaring an International Mother Language Day. Rafiq proposed the date as 21 February to commemorate the 1952 killings in Dhaka during the Language Movement."21st February – The International Mother Language Day"