The Ganges runs from the western Himalayas to the Bay of Bengal
The World Bank has agreed to lend India $1bn (£600m) over the next five years to clean up the Ganges, one of the most polluted rivers in the world.
The 2,500km (1,500-mile) river has been badly polluted by industrial chemicals, farm pesticides and other sewage.
Speaking in Delhi, World Bank chief Robert Zoellick said the clean-up would target the entire river network.
Plans involve building sewage treatment plants, revamping drains and other measures to improve the water quality.
The funding is part of the Indian government's multi-billion dollar initiative to end the discharge of untreated waste into the Ganges by 2020.
Environmentalists say the river supports more than 400 million people, and if the unabated pollution is not controlled, it will be the end of communities living along the banks.
Earlier attempts to clean the river have failed, including a plan to make its water drinkable by 1989.
But Mr Zoellick said he was confident the plan would work this time.
"In the past, [efforts] focused too much on individual aspects such as sewage emissions and not enough on the basin as a whole," he said.
"What really distinguishes this project is to try to look at the whole river network and try to deal with all the aspects."
Correspondents say many of India's polluting factories are located on the banks of the Ganges and their effluent has been largely responsible for the pollution of the river.
The Ganges also flows through some of most crowded cities of India which release their untreated sewage into the river.
Also on Wednesday, India's finance ministry said the World Bank would triple its lending to $7bn this year for development, infrastructure and other projects.