promises of a surge in economic growth.
With 814 million eligible voters, India will vote in stages over the next five weeks in a staggered approach made necessary by the country's vast size. Voters will choose representatives for the 543-seat lower house of parliament.
Results from all 935,000 polling stations are expected on May 16. The opposition Bharatiya Janata Party and its candidate for prime minister, Narendra Modi, are seen as the biggest threats to the now-governing Congress party.
BJP is expected to do well but to fall short of a 272-seat majority, making a coalition government a likely outcome, observers say.
"I've made it a point to vote this time because we want change," said 36-year-old housewife Rumi Nath, waiting to vote in the rural town of Lakhimpur on the Brahmaputra River. "Our area remains backward and underdeveloped 67 years after independence."
Polls suggest Congress could face a drubbing due to corruption scandals and recent years of economic slowdown. The BJP's Modi has been credited with ushering in strong industrial growth in the western state of Gujarat, where he has been chief minister for 11 years.
The election will be key to the future of the family dynasty that has ruled India for much of its post-independence history.
The Nehru-Gandhi family is facing its biggest political threat in over a decade, with Rahul Gandhi, the 43-year-old family scion, leading the Congress's struggling campaign. While Gandhi has been presented to voters as a youthful leader who can rejuvenate India's faltering economy.