He was 78. The Bengali writer is survived by wife and son.
Gangopadhyay's body will be kept in a mortuary till his son arrives from Boston for performing the last rites, his family said.
Winner of the Sahitya Akademi Award in 1985 for his historical novel 'Sei Samoy' (At That Time), Gangopadhyay's best-selling works include 'Pratham Alo' and 'Purbo-Paschim', a depiction of Partition and its aftermath seen through the eyes of three generations of Bengalis in West Bengal, Bangladesh and elsewhere.
He also received the 'Ananda Puraskar' twice, the 'Bankim Puraskar' and Hindu Literary Prize.
Condoling his death, President Pranab Mukherjee said "Gangopadhyay enriched Bengali literature through his unique style. He was the greatest among his peers. A bright star has fallen.
The vacuum created by his death cannot be filled."
Eminent writers, including Shirshendu Mukhopadhyay, Samaresh Majumdar, Nirendranath Chakrabarty and Abul Bashar mourned his death.
Using the pen-names of Nil Lohit, Sanatan Pathak and Nil Upadhyay, Gangopadhyay was the author of over 200 books and excelled in different genres, but declared poetry to be his first love.
His well-known poems include 'Kavita Sangraha', 'Shada Pristha Tomar Sangay' and 'Amar Swapna'. His Neera series of poems were also popular.
Gangopadhyay was the founder editor of 'Krittibas', a seminal poetry magazine that became a platform for a new generation of poets experimenting with many new forms.
His novels like 'Aranyer Din Ratri', 'Pratidhwani and 'Arjun' were made into films by maestro Satyajit Ray and 'Abar Aranya' by Gautam Ghosh. His other work of prose include the adventurous character for young adults 'Kakababu'.
Born in Faridpur (Bangaldesh) on September 7, 1934, Gangopadhyay was also known for short stories like 'Shreshtha Galpo' and 'Maha Prithibi'. MORE