The National Social Security Institute (NSSI) is the public institution that manages the state social security in Republic of Bulgaria. NSSI administrates the compulsory social security for sickness, maternity, unemployment, accident at work and professional diseases, disability, old age and death. It is the competent institution of Bulgaria in coordination with the social security for EU and the implementation of bilateral agreements in the fields of sickness and maternity benefits, death grants, unemployment benefits and pensions for disability, old age and survivors.

The National Social Security Institute was created in 1995 by the Law for State Social Security Fund as a successor of the Head Office of Social Security. NSSI reports its activities at the National Assembly of the Republic of Bulgaria. The Supervisory Board is the highest management body of NSSI comprised of representatives of the State and the national representative organizations of workers and employers.

The National Social Security Institute is a legal entity composed of a Head Office in Sofia city and local offices in each of the 28 district centers of the country