The Census of population, households and apartments in the Republic of Croatia in 2021 (Croatian: Popis stanovništva, kućanstva i stanova u Republici Hrvatskoj 2021. godine; shortened: Census 2021, Popis 2021.)

The census recorded a resident population of 3,871,833 in the twenty counties and the City of Zagreb, a decrease of 9.64 percent, or 413,056 over the preceding decade.

[2] The Census collects the following data:[3] A population decline was recorded in each of 20 counties and the City of Zagreb.

On the other hand, Zagreb had a large influx of citizens from other parts of Croatia, giving it the smallest relative change.

[2] Croatian citizens by first language, including non-official recognized Serbo-Croatian and Croato-Serbian:[2] Sex and age structure of the population of Croatia:[2]