The report by the French Institute of Demographic Studies (INED), predicts India will take the top spot with a staggering population of 1.6 billion to leave behind current world leader in population, China, at the second place with 1.3 billion people.
The overall world population is projected to rise to 9.7 billion in 2050 from the current level of 7.1 billion, the report said.
Currently, the world's most populous countries are China with 1.3 billion people; followed by India (1.2 billion); the US (316.2 million); Indonesia (248.5 million) and Brazil (195.5 million).
In June, a UN study predicted the global population to swell to 9.6 billion in 2050.
"The world population has risen seven-fold over the last two hundred years and is expected to reach 10 or 11 billion by the end of the twenty-first century," according to the report by Gilles Pison, senior researcher at the French institute.
According to the report, the projected population of other countries in the world by 2050 (in millions) will be: Nigeria (444), US (400), Indonesia (366), Pakistan (363), Brazil (227), Bangladesh (202), Congo (182), Ethiopia (178), Philippines (152), Mexico (150), Russia (132), Tanzania (129), Egypt (126), Uganda (114), Vietnam (109), Iran (99), Japan (97), Kenya (97), Turkey (93), Iraq (83), UK (79), Germany (76), France (72), Sudan(69), Niger(66), South Africa (64), Mozambique (63) and Colombia (63).