Direct Action Day, also known as the Great Calcutta Killings, was a day of widespread communal violence that occurred on August 16, 1946, in the city of Calcutta (now Kolkata), India. It was organized by the Muslim League as a call for the creation of a separate Muslim-majority state, later known as Pakistan.

Tensions between Hindus and Muslims had been escalating due to the political divide over the demand for Pakistan. The Muslim League had called for a day of strike and protest to assert their demand, while the Hindu nationalist group, the Hindu Mahasabha, had called for a counter-protest.

On Direct Action Day, the streets of Calcutta were filled with violent clashes, looting, and arson. Rioting continued for several days, resulting in the deaths of an estimated 4,000 people and the displacement of thousands more.

Mahatma Gandhi, who was a strong advocate for Hindu-Muslim unity, was deeply saddened by the violence. He traveled to Calcutta in an attempt to restore peace and calm the situation. Gandhi's efforts, along with the intervention of other leaders, eventually led to the restoration of peace in the city.

Direct Action Day is seen as a significant event in the lead-up to the partition of India in 1947 and the subsequent creation of Pakistan. It highlighted the deep communal tensions and the challenges of maintaining unity in a diverse society like India.