Vinayak Damodar Savarkar (1883-1966) was an early ideologue of the Hindu Nationalist movement who coined the term "Hindutva". Writing in Hindutva: Who is a Hindu?, an important early text of the Hindu nationalist movement, Savarkar set out his vision of a nationalism based on religion, territory, language, culture and "race". He wrote, for example, "Hindutva embraces all the departments of thought and activity of the whole Being of our Hindu race".
Savarkar was a leader of the Hindu Mahasabha. Mahatma Gandhi's assassin, Nathuram Godse, was close to Savarkar, and the government initially filed charges against Savarkar for the murder. Although these were dropped, later evidence revealed that Savarkar was indeed central to the conspiracy.
Narendra Modi has often expressed his deep admiration for Savarkar.
References:
• Hindu Nationalism: A Reader Edited by Christophe Jaffrelot, Princeton, 2007.