International Nuclear Safety Advisory Group (INSAG) was established in 1985 within IAEA to discuss the matters related to and to exchange informations concerning nuclear safety. INSAG has published several reports based on their activities, one of which was a summary report on the Post-accident Review Meeting on the Chernobyl Accident. “Basic Safety Principles for Nuclear Power Plants (BSP)” is the third report of the series.BSP summarizes the safety principles which are to be followed by all of personnels working in nuclear community including designers and owners of the plants and regulators. Special emphasis is given to the concept of “Safety Culture” which forms the basis of assuring the safety of the plant. Severe accident is also given a special attention since an accident leading to release of a large amount of radioactive materials must be prevented and measures to mitigate such accident are provided.The background and objectives of BSP are explained in the present document.