Bal Gangadhar Tilak (July 2, 1856-August 1, 1920) was a political activist for Indian independence who was imprisoned for his activities. He was also a prominent Hindu thinker.

Although he was basically a proponent of Advaita Vedanta, he differed from the classical Advaitin view that jnana (knowledge) alone brings release. Tilak added a measure of karma-yoga (the yoga of activity) to this, not as subordinate to jnana-yoga , but as equal and complementary to it.

Tilak proposed various social reforms, such as a minimum age for marriage, and was especially keen to see a prohibition placed on the sale of alcohol. His thoughts on education and Indian political life have remained highly influential — he was the first Congress leader to suggest that Hindi, written in the devanagari script, should be accepted as the sole national language of India, a policy that was later strongly endorsed by Gandhi. However, English, which Tilak wished to remove completely from the Indian mind, remains an important means of communication in India. But the usage of Hindi (and other Indian languages) has been reinforced and widely encouraged since the days of the British Raj, and Tilak's legacy is often credited with this resurgence.

As a political activist, Bal Gangadhar Tilak helped garner support for India's independence movement. In one of his speeches, he declared famously "Swaraj (Self-rule) is my birthright, and I shall have it!" At that time, in the late 1800s, the primary focus of the movement was for self-rule. In 1906, Tilak would ask Jinnah to represent him during Tilak's trial for sedition against the British Empire. It was only later (in the 1910s) that the focus of the movement changed to complete independence.

Tilak authored The Orion in which he used astronomy to establish that the Vedic people were present in India at least as early as the 4th millennium BC.