Kozloduy nuclear power plant is the first nuclear power plant in Bulgaria and south-eastern Europe.
The beginning of the nuclear power engineering was laid on 15 July 1966 by signing the agreement for cooperation between Bulgaria and former Soviet Union for the construction of a nuclear power plant. Following a detailed feasibility study the site on the Danube river was selected in the proximity of the town of Kozloduy.
The designs for the plant were developed by Toploelektroproekt – Moscow and Energoproekt – Sofia. The main equipment was delivered by the Soviet Union, and some separate pieces of equipment from the former German Democratic Republic , Czechoslovakia and Hungary. The ground breaking ceremony for Kozloduy NPP was held on 14 October 1969. In April 1970 the large scale construction activities for the facility, still unique for the country in the present days, started. More than one hundred thousand construction and installation workers took part in the construction.
Some completely Bulgarian projects have been implemented for the first time in the world practice in the construction of nuclear power plants. Some of these technical solutions are significant engineering achievements foreign specialists have been interested in.
The construction of the main building of Kozloduy NPP started on 6 April 1970 -240 m long, 105 m wide and 40 m high. The reactor hall, turbine hall, ventilation center and the electrical devices of the 440 MW units are inside this building. In June 1972 the first reactor arrives from the Soviet Union, and on 20 November same year it was installed into the reactor cavity.

The construction and commissioning of the Bulgarian nuclear power plant was implemented in three stages:

• І stage: 1970 – 1975 Construction and commissioning of unit 1 and 2 with VVER-440 , model В-230, with two independent trains of the safety systems.
  Start-up of Unit 1: 1974
  Start-up of Unit 2:1975
  The official opening of Kozloduy NPP was on 4 September 1974.
• ІІ stage: 1973 – 1982 Construction and commissioning of Units 3 and 4 with VVER-440, upgraded model В-230 with three-fold redundancy of the safety systems .
  Start-up of Unit 3: 1980
  Start-up of Unit 4: 1982
• ІІІ stage: 1980 – 1991 Construction and commissioning of Units 5 and 6 with VVER-1000, model В-320 with containment and three-fold redundancy of the safety systems.
  Start-up of Unit 5: 1987
  Start-up of Unit 6: 1991
  

Following the commitments made by Bulgaria with regard to the accession to the EU, Kozloduy NPP stopped the operation of the first four units before the expiry of their design lifetime that is 30 fuel campaigns.

Since the beginning of 2007 Units 5 and 6 have remained in operation.