The demography of the Republic of Bulgaria is monitored by the National Statistical Institute of Bulgaria. Demographic features of the population of Bulgaria include population density, ethnicity, education level, health of the populace, economic status, religious affiliations and others.

The People's Republic of Bulgaria was the official name of Bulgaria when it was a socialist republic from 1946 to 1990, ruled by the Bulgarian Communist Party (BCP) together with its coalition partner, the Bulgarian Agrarian People's Union. Bulgaria was closely allied and one of the most loyal satellite states of the Soviet Union during the Cold War, sometimes being called the 16th Soviet Republic rather than an independent country. Bulgaria was also part of Comecon as well as a member of the Warsaw Pact. The Bulgarian resistance movement during World War II deposed the Kingdom of Bulgaria administration in the Bulgarian coup d'état of 1944 which ended the country's alliance with the Axis powers and led to the People's Republic in 1946.