Currently, about 1.31 billion people live in India, compared with approximately 1.38 billion in China.
The Indian population will continue growing for decades after 2022 and will reach 1.5 billion by 2030 and 1.7 billion by 2050, while China's population will remain more or less stable until 2030 and will then begin to decline, the UN said.
The projections also are that by 2050 Nigeria may surpass the US and become the world's third-most populous country, according to estimates made public on Wednesday by the United Nations.
The UN says that the African nation will register the largest population increase among the world's big countries, growing from its current 182 million to more than 262 million by 2030 and almost 400 million by 2050.
The US, which currently has almost 322 million people, will continue growing, although more slowly, and by 2050 its population is estimated to stand at about 389 million.
According to the UN, during the coming decades the growth of the world population will be concentrated mainly in nine countries: India, Nigeria, Pakistan, the Democratic Republic of the Congo, Ethiopia, Tanzania, the US, Indonesia and Uganda.
With the highest demographic growth rate, Africa will contribute more than half of the increase in the planet's population between 2015 and 2050.
The population of Latin America and the Caribbean, meanwhile, will increase from the current 634 million to 721 million by 2030 and 784 million by 2050 but will then begin to decline, falling back to about 721 million by the end of the century.
Latin America will experience a clear ageing of its population in the coming decades and in 2050 people over age 60 will make up a quarter of the population, compared with only a little over 11 percent now.
Brazil and Mexico, which are currently among the world's 10 most populous countries, will continue growing until 2050, when their populations will stand at 238 million and 164 million, respectively.
In total, according to these estimates, the world will expand from its current 7.3 billion inhabitants to 8.5 billion by 2030, about 9.7 billion by 2050 and around 11.2 billion by the end of this century.