The Constitution of Croatia in its preamble defines Croatia as a nation state of ethnic Croats, a country of traditionally present communities that the constitution recognizes as national minorities and a country of all its citizens. National minorities explicitly enumerated and recognized in the Constitution are Serbs, Czechs, Slovaks, Italians, Hungarians, Jews, Germans, Austrians, Ukrainians, Rusyns, Bosniaks, Slovenes, Montenegrins, Macedonians, Russians, Bulgarians, Poles, Romani, Romanians, Istro-Romanians ("Vlachs"), Turks and Albanians. Article 12 of the constitution states that the official language in Croatia is Croatian, but also states that in some local governments another language and Cyrillic or some other script can be introduced in official use.

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.