In 2021, Portugal registered a resident population of 10,347,892 people, marking the largest population decrease in the last 50 years, according to the census results released by the National Statistics Institute (INE).
This was a decrease of 2 per cent compared to 2011, Xinhua news agency quoted the census results released on Wednesday as saying.
Last year's figure was also 214,286 fewer residents compared to the past decade, according to INE.
"In terms of the census, the only decade in which there was a decrease in population was between 1960 and 1970," the INE said in a statement.
According to an analysis by INE President Francisco Lima, Portugal registered a positive migration balance, but that "was not enough to compensate" for the reduction in the country's population in the last 10 years.
According to Lima, only the regions of Lisbon and Algarve, in the south of Portugal, registered an increase in population, indicating that "there is a clear concentration around the capital" of the country, with "inland territories losing population".
The census was carried out between April 5 and May 31, with 99.3 per cent of the population's responses arriving through digital internet channels.