Croatia is territorially about twice the size of Belgium, but with 3,9 million inhabitants (2021 census) it has just over a third of its population. Croatia is the 19th country in Europe according to territory, between Latvia and Slovakia, and 20th according to population, between Ireland and Lithuania.

In the last 150 years, several factors have influenced population development, the most important of which important are continual, sometimes intensive, emigration to European and more distant destinations, two world wars and the Homeland War.

Although the population of Croatia has almost doubled in the last 160 years (1857–2021), this is low in comparison to other countries (for example, the population of The Netherlands increased 5.3 times in the same period). The population has on the whole increased, with a particularly high rate at the end of the 19th century, when it entered the first phase of demographic transition, marked by high rates of natural change. However, in the early 20th century emigration increased, and the rate of population growth fell, while the outbreak of the First World War and the Spanish Flu epidemic led to the first actual decrease in the population. After recovering slightly in the 1920s, war again followed, and there was a second fall in population levels. The growth of the population from the 1960s to the 1980s was slowed by a decrease in natural change, directly linked to a decrease in the birth rate, accompanied by marked emigration for 'temporary work' abroad. In these circumstances, the population of Croatia went through an accelerated demographic transition. By the end of the 1980s, a low rate of natural change was noted, which was not at all in line with the rate of economic development. With such a weakened (particularly reproductive) population base, Croatia faced yet another war in the 1990s, followed by an insecure post-war period, the consequence of which was a third drop in population numbers at the turn of the 21st century. This decline has further been intensified by emigration, mostly to Germany, Ireland and Austria, after Croatia became a member of the European Union. According to the 2021 census, a total of 3,9 million people live in the country, with a population density of 68 people per km².

Population trends, 1857–2021
The age-gender composition of the population to a great extent reflects a typical European process – demographic ageing.
Natural population trends 1950–2020

A long period of depopulation has resulted in many negative consequences, such as the reduction of the core population producing new generations, the reduction of the active working population, and the increasing care needs of the older population; in other words, increased economic and social burdens placed on the State Budget in the areas of pension insurance, social and health care of the elderly, etc.

Apart from the decreasing population, the contemporary demographic picture of Croatia is much like those of the other members of the EU. It is characterised by three processes: ageing, natural depopulation, and spatial polarisation of the population.

Life expectancy has risen to 81 for women and 75 for men, leading to the more rapid ageing of the population. The average age, which was 30.7 sixty years ago, has risen to 44.3. Almost one quarter of the population of Croatia today is over 65 years old (22%), while fifty years ago, it was 12%. In addition, only 14% of the population today is of elementary school age, while it was 27% in the early 1960s. Natural depopulation is closely related to the process of population ageing, or rather the decrease in the population due to the death rate being higher than the birth rate, and the fall in the average number of children per woman of fertile age (1.5), which puts Croatia side by side with other European countries.

This natural change of -6.8‰, like other demographic processes in Croatia, goes back several decades. The birth rate has been falling constantly since the 1950s, the death rate has been rising since the 1970s, while in the 1990s, when the death rate increased due to war losses, the figures for natural change were also negative.

On Croatian initiative, the question of demographic revitalisation has been inserted into the European Union's strategic agenda until 2024. In addition, Croatian europarliamentarian Dubravka Šuica began her five-year mandate as Vice-President of the European Commission for Democracy and Demography in 2019.