Bal Gangadhar Tilak (pronunciation^ⓘ; born Keshav Gangadhar Tilak (pronunciation: [keʃəʋ ɡəŋɡaːd̪ʱəɾ ʈiɭək]); 23 July 1856 – 1 August 1920), endeared as Lokmanya (IAST: Lokamānya), was an Indian nationalist, teacher, and an independence activist. He was one third of the Lal Bal Pal triumvirate. The British colonial authorities called him "The father of the Indian unrest". He was also conferred with the title of "Lokmanya", which means "accepted by the people as their leader". Mahatma Gandhi called him "The Maker of Modern India".

Tilak was one of the first and strongest advocates of Swaraj ('self-rule') and a strong radical in Indian consciousness. He is known for his quote in Marathi: "Swaraj is my birthright and I shall have it!". He formed a close alliance with many Indian National Congress leaders including Bipin Chandra Pal, Lala Lajpat Rai, Aurobindo Ghose, V. O. Chidambaram Pillai and also Muhammad Ali Jinnah who later oversaw Pakistan's independence from British rule.^{[citation needed]}

Keshav Gangadhar Tilak was born on 23 July 1856 in a Marathi Hindu Chitpavan Brahmin family in Ratnagiri, the headquarters of the Ratnagiri district of present-day Maharashtra (then Bombay Presidency). His ancestral village was Chikhali. His father, Gangadhar Tilak was a school teacher and a Sanskrit scholar who died when Tilak was sixteen. In 1871, Tilak was married to Tapibai (Née Bal) when he was sixteen, a few months before his father's death. After marriage, her name was changed to Satyabhamabai. He obtained his Bachelor of Arts in first class in Mathematics from Deccan College of Pune in 1877. He left his M.A. course of study midway to join the L.L.B course instead, and in 1879 he obtained his L.L.B degree from Government Law College. After graduating, Tilak started teaching mathematics at a private school in Pune. Later, due to ideological differences with the colleagues in the new school, he withdrew and became a journalist. Tilak actively participated in public affairs. He stated: "Religion and practical life are not different. The real spirit is to make the country your family instead of working only for your own. The step beyond is to serve humanity and the next step is to serve God."

Inspired by Vishnushastri Chiplunkar, he co-founded the New English school for secondary education in 1880 with a few of his college friends, including Gopal Ganesh Agarkar, Mahadev Ballal Namjoshi and Vishnushastri Chiplunkar. Their goal was to improve the quality of education for India's youth. The success of the school led them to set up the Deccan Education Society in 1884 to create a new system of education that taught young Indians nationalist ideas through an emphasis on Indian culture. The Society established the Fergusson College in 1885 for post-secondary studies. Tilak taught mathematics at Fergusson College. In 1890, Tilak left the Deccan Education Society for more openly political work. He began a mass movement towards independence by an emphasis on a religious and cultural revival.

Tilak had a long political career agitating for Indian autonomy from British colonial rule. Before Gandhi, he was the most widely known Indian political leader. Unlike his fellow Maharashtrian contemporary, Gokhale, Tilak was considered a radical Nationalist but a Social conservative. He was imprisoned on a number of occasions that included a long stint at Mandalay. At one stage in his political life he was called "the father of Indian unrest" by British author Sir Valentine Chirol.

Tilak joined the Indian National Congress in 1890. He opposed its moderate attitude, especially towards the fight for self-government. He was one of the most-eminent radicals at the time. In fact, it was the Swadeshi movement of 1905–1907 that resulted in the split within the Indian National Congress into the Moderates and the Extremists.

During late 1896, a bubonic plague spread from Bombay to Pune, and by January 1897, it reached epidemic proportions. The British Indian Army was brought in to deal with the emergency and strict measures were employed to curb the plague, including the allowance of forced entry into private houses, the examination of the house's occupants, evacuation to hospitals and quarantine camps, removing and destroying personal possessions, and preventing patients from entering or leaving the city. By the end of May, the epidemic was under control. The measures used to curb the pandemic caused widespread resentment among the Indian public. Tilak took up this issue by publishing inflammatory articles in his paper Kesari (Kesari was written in Marathi, and "Maratha" was written in English), quoting the Hindu scripture, the Bhagavad Gita, to say that no blame could be attached to anyone who killed an oppressor without any thought of reward. Following this, on 22 June 1897, Commissioner Rand and another British officer, Lt. Ayerst were shot and killed by the Chapekar brothers and their other associates. According to Barbara and Thomas R. Metcalf, Tilak "almost surely concealed the identities of the perpetrators". Tilak was charged with incitement to murder and sentenced to 18 months imprisonment. When he emerged from prison in present-day Mumbai, he was revered as a martyr and a national hero. He adopted a new slogan coined by his associate Kaka Baptista: "Swaraj (self-rule) is my birthright and I shall have it."

Following the Partition of Bengal, which was a strategy set out by Lord Curzon to weaken the nationalist movement, Tilak encouraged the Swadeshi movement and the Boycott movement. The movement consisted of the boycott of foreign goods and also the social boycott of any Indian who used foreign goods. The Swadeshi movement consisted of the usage of natively produced goods. Once foreign goods were boycotted, there was a gap which had to be filled by the production of those goods in India itself. Tilak said that the Swadeshi and Boycott movements are two sides of the same coin.