A preliminary tally of Japan's census, released every five years, found that the population slipped to 123 million people in 2025 -- more than three million fewer than when the survey was last carried out in 2020.
It was the biggest decrease since the twice-a-decade survey started in 1920, and more than triple the decline recorded between 2015 and 2020.
The data "once again confirmed the population decline in our nation is deepening," top government spokesman Minoru Kihara told reporters.
Japan has one of the world's lowest birth rates and an ageing population.
While immigration is often floated as a solution to Japan's shrinking demographic, Prime Minister Sanae Takaichi is pushing for tougher measures against an inflow of foreigners.
