The vessel, with about 60 people on board, turned over in the fast-flowing water, the senior supervising police officer Brij Lal told AFP from Uttar Pradesh state capital Lucknow.
Lal said 47 had died, including 15 men, 14 women and 18 children.
The accident occurred in Ballia district, 400 km southeast of Lucknow, when families hired the boat to perform a religious ceremony on the river, which is sacred to Hindus.
"The tragedy apparently occurred on account of overloading of the boat, which did not have the capacity to carry more than 25 persons," he said.
“As the boat entered the midstream it failed to take the weight of the people and collapsed,” added another police official.
Boat tragedies are common in the impoverished state.
Vessels used to ferry passengers are generally rickety and overcrowded and people seldom use life jackets.
