India has joined a handful of countries that can deploy a nuclear-powered submarine.
The 8,000 tonne INS Chakra was formally commissioned into the Indian Navy in a ceremony at Vishakhapatnam off the Bay of Bengal on Wednesday.
The submarine is on a 10-year lease from Russia but, in accordance with non-proliferation treaties, will not be carrying nuclear weapons.
India previously had a Soviet submarine but decommissioned it in 1991. It now rejoins China, Russia, the United States, the United Kingdom and France as an operator of underwater nuclear vessels.
Its first home-produced submarine is expected to enter service in 2013.