Russian biathlete and two-time Olympic gold medalist, he won gold in the 4 x 7.5 km relay and the 20 km individual events in 1976.
He won his first gold medal in International Competition at the 1975 World Championships.
He won a total of five gold medals between the Olympics and World Championships.
His son, Nikolay Kruglov, Jr., is also a biathlete.
He won two golds in 1976, the same year Dorothy Hamill won gold in figure skating.