The demographic characteristics of the population of Croatia are known through censuses, normally conducted in ten-year intervals and analysed by various statistical bureaus since the 1850s. The Croatian Bureau of Statistics has performed this task since the 1990s. The latest census in Croatia was performed in autumn of 2021. According to final results published on 22 September 2022 the permanent population of Croatia at the 2021 census had reached 3.87 million. The population density is 68.7 inhabitants per square kilometre, and the overall life expectancy in Croatia at birth was 78,2 years in 2018. The population rose steadily from 2.1 million in 1857 until 1991, when it peaked at 4.7 million. Since 1991, Croatia's death rate has continuously exceeded its birth rate; the natural growth rate of the population is negative. Croatia is in the fourth stage of the demographic transition. In terms of age structure, the population is dominated by the 15 to 64 year‑old segment. The median age of the population is 43.4, and the gender ratio of the total population is 0.93 males per 1 female.

The term Vlachs was initially used in medieval Croatian and Venetian history for a Romance-speaking pastoralist community, called "Vlachs" and "Morlachs", inhabiting the mountains and lands of the Croatian Kingdom and the Republic of Venice from the early 14th century. By the end of the 15th century they were highly assimilated with the Slavs and lost their language or were at least bilingual, while some communities managed to preserve and continue to speak their language (Istro-Romanians).