The population of Argentina has increased 20-fold since 1869, when 1.9 million people were recorded there by the first census. Population growth was rapid through the early part of the 20th century, but it declined thereafter as both the birth rate and immigration began to drop off; the proportion of young people also declined. Argentina's rates of birth and population growth are now among South America's lowest. The nation's population density is also among the continent's lowest.

Heavy immigration, particularly from Spain and Italy, has produced in Argentina a people who are almost all of European ancestry. In the colonial time, though, the Spanish explorers and settlers encountered a number of native peoples. Among these were the Diaguita tribes of the Andean Northwest, a town-dwelling, agricultural people who were forced into labour after they had been conquered. They were separated by the Spanish into small groups and were sent to work in Peru and the Río de la Plata area. In the Mesopotamian region the semiagricultural Guaraní also were forced into labour.

Argentines are a fusion of various national and ethnic groups, with descendants of Italian and Spanish immigrants predominant. Waves of immigrants from many European countries arrived in the late 19th and early 20th centuries. Syrian, Lebanese, and other Middle Eastern immigrants number about 501,000, mainly in urban areas. Argentina's population is overwhelmingly Catholic, but it also has the largest Jewish population in Latin America, about 250,000 strong, and is home to one of the largest Islamic mosques in Latin America. In recent years, there has been a substantial influx of immigrants from neighboring Latin American countries. The indigenous population, around at 700,000, is concentrated in the provinces of the north, northwest, and south. The Argentine population has one of Latin America's lowest growth rates. 80 % of the population resides in cities or towns of more than 2,000, and over 1/3 lives in the greater Buenos Aires area. With 13 million inhabitants, this sprawling metropolis serves as the focus for national life.