The United Nations estimates India's population will be 1.4286 billion by the middle of 2023 — ahead of the 1.4257 billion it sees for mainland China's population.
The figures are now reflected in the UN's World Population Dashboard, updated on Wednesday.
The overtake has been widely-predicted as China's population growth has slowed, with the number of people last year falling for the first time since the early 1960s.
The U.N. has previously forecast China's population will decline to 1.313 billion by 2050 and fall below 800 million by 2100.
Experts have said the country's longstanding one-child policy, which was revised to two in 2016 and three in 2021, contributed to the decline.
The U.N. figures exclude the "special administrative regions" of Hong Kong, which it estimates at 7.5 million, and Macao, at 0.7 million.
India's population growth has averaged 1.2% since 2011, down from 1.7% the previous decade, according to government data cited by Reuters.
The U.N. figures show 26% of the the population is aged 10-24, versus 18% in China.
India's most recently-published census data is from 2011.
In its State of World Population 2023 report, published Wednesday, the United Nations Population Fund addresses the world population surpassing 8 billion people in November 2022, and cautions against erasing human rights and autonomy in discussions about whether population growth is a concern.
"Human reproduction is neither the problem nor the solution" to challenges such as climate change, pandemics, conflicts, mass displacement and economic uncertainty, said the body's Executive Director Natalia Kanem.