September 21 is an important date in Indian history, particularly for the political integration of the Northeast and the contributions of personalities from literature, cinema, social activism and sports. One of the major events associated with the date is the Manipur Merger Agreement of 1949, signed by Maharaja Bodh Chandra Singh and V. P. Menon at Shillong.

The agreement provided for the transfer of Manipur's administration to the Government of India, with the administration formally taken over on October 15, 1949.
The date is also associated with the birth anniversaries of several prominent Indians, including Gurajada Apparao, Maharaja Hari Singh, Singeetam Srinivasa Rao, Swami Agnivesh, Gulshan Grover and Kareena Kapoor. Indian cricket has also had several personalities born on September 21, including Ranjib Biswal, Kiran Mokashi and Ajitesh Argal.
Manipur Merger Agreement Signed in 1949
On September 21, 1949, the Manipur Merger Agreement was signed at Shillong between Maharaja Bodh Chandra Singh of Manipur and V. P. Menon, Adviser to the Government of India. Under the agreement, the Maharaja ceded authority and jurisdiction over the state's governance to the Dominion Government, with the administration scheduled to be transferred on October 15, 1949.
The merger remains an important and historically debated subject in Manipur. Historical records establish the date and terms of the agreement, while different interpretations of the political circumstances surrounding the merger continue to exist.
Bahadur Shah Zafar Surrenders in 1857
September 21, 1857, is also associated with the surrender of Bahadur Shah Zafar, the last Mughal emperor, to the British following the fall of Delhi during the Revolt of 1857. His capture marked another major turning point in the uprising against British East India Company rule.
Gurajada Apparao
Telugu playwright, poet and writer Gurajada Venkata Apparao was born on September 21, 1862. He is remembered for his contribution to Telugu literature and theatre and for works that addressed social issues.
Maharaja Hari Singh
Hari Singh, the last ruling Maharaja of Jammu and Kashmir, was born on September 21, 1895. He remained an important figure in the political history of Jammu and Kashmir.
Singeetam Srinivasa Rao
Film director, screenwriter, producer and composer Singeetam Srinivasa Rao was born on September 21, 1931. He has worked extensively in South Indian cinema and is known for his innovative filmmaking.
Swami Agnivesh
Social activist Swami Agnivesh was born on September 21, 1939. He was known for his work on social justice, bonded labour and other public issues.
September 21 is also the birthday of actor Gulshan Grover (1955), actress Kareena Kapoor (1980), actor Akshay Dogra (1981), actor Karunakaran (1981) and filmmaker Atlee Kumar (1986).
Several Indian political figures were born on September 21. They include Hari Singh, U. N. Dhebar, Satpal Maharaj, Vivek Tankha, Ram Shankar Katheria, Rajiv Satav and Alka Lamba.
Hari Singh is particularly significant in the political history of Jammu and Kashmir, while U. N. Dhebar served as president of the Indian National Congress.
Several Indian cricketers and cricket personalities share their birthdays on September 21. These include:
September 21 is remembered for the death anniversary of Raju Srivastava, the popular Indian comedian, actor and politician, who died on September 21, 2022, at the age of 58. His death was widely mourned across India's entertainment industry.
Naramalli Sivaprasad, an Indian actor and politician, also died on September 21, 2019.
The International Day of Peace is observed every year on September 21. The United Nations General Assembly established the date as an annual day devoted to strengthening the ideals of peace and non-violence. In 2001, the General Assembly unanimously adopted a resolution establishing September 21 as a day of non-violence and ceasefire.
World Alzheimer's Day is observed annually on September 21 to raise awareness about Alzheimer's disease and other forms of dementia. The day highlights the importance of understanding dementia, supporting affected people and families, and promoting awareness about brain health.
September 21 has a significant place in India's historical calendar because of the Manipur Merger Agreement of 1949 and events connected with the Revolt of 1857. The date also celebrates personalities from literature, cinema, social reform and politics, including Gurajada Apparao, Hari Singh, Singeetam Srinivasa Rao, Swami Agnivesh and Kareena Kapoor.
The date has an international significance as the International Day of Peace, while World Alzheimer's Day draws attention to dementia awareness. Together, these historical events, personalities and observances make September 21 an important date in India's historical and global calendar.