The Indian National Congress (also called the Congress Party) is the oldest surviving political organisation in India. It is one of the largest political parties in India. It played a major role in the Indian independence movement, and was the ruling party in most of independent India's governments.
It was founded in 1885 with the object of obtaining a greater share in government for educated Indians, and was initially not opposed to British rule. Indeed, it was an Englishman, Allan Octavian Hume who brought about its first meeting in Bombay, with the approval of Lord Dufferin, the then Viceroy. Later, however, its demands became more radical in the face of constant opposition from the government, and became very active in the independence movement. During this period there were two camps in the Congress -- the Garam Dal or Extremists and the Naram Dal or Moderates -- depending on their attitude towards the British. Its leaders before Indian independence included Mohandas Gandhi (aka Mahatma Gandhi), Subash Chandra Bose (also known as Netaji S. C. Bose).
Gandhi is said to have held the view that the party was formed only for independence and must have been disbanded in 1947. But the party ruled India for much of the time after independence under Jawaharlal Nehru, Nehru's daughter Indira Gandhi, her son Rajiv Gandhi, P. V. Narasimha Rao among others.
In the 1980s and 1990s it was also known as Congress-I where the I stood for Indira (initially to distinguish it from Congress-O led by Kamaraj, etc.). Slowly many groups broke away from the Congress and there are now scores of parties each derived from the Congress and hence having 'Congress' somewhere in their party name, thus decreasing somewhat the strength of the Congress from the 1940s to 60s when it used to regularly get two-thirds majority in Parliament.
It is currently the main opposition party at the Center (i.e. the central or federal government) and also has formed the government in a majority of Indian states. Its current leader is Sonia Gandhi, wife of the former Prime Minister Rajiv Gandhi.
Currently there is some controversy about the foreign (Italian) origin of Sonia Gandhi which raises doubts about the appropriateness of her becoming the Prime Minister if the party returns to power.