In January 2020, the municipality of Madrid, capital of Spain, had a population of 3,345,894 registered inhabitants[1] in an area of 604.3 square kilometers (233.3 sq mi).

The population of Madrid has overall increased since the city became the capital of Spain in the mid-16th century, and has stabilised at approximately 3 million since the 1970s.

The demographic boom accelerated in the late 1990s and early first decade of the 21st century due to immigration in parallel with a surge in Spanish economic growth.

[8] According to a 2019 Centro de Investigaciones Sociológicas (CIS) survey with a sample size of 469 respondents, 20.7% of respondents in Madrid identify themselves as practising Catholics, 45.8% as non-practising Catholics, 3.8% as believers of another religion, 11.1% as agnostics, 3.6% as indifferent towards religion, and 12.8% as atheists.

[9] According to Eurostat, the "metropolitan region" of Madrid has a population of slightly more than 6,271 million people[10] covering an area of 4,609.7 square kilometres (1,780 sq mi).