Nygaard spent his youth on the farm of his uncle, where he had mitsorgen during the war for the survival of the family. Nevertheless, he was presented with 14 employees of the Institute for Astrophysics, University of Oslo. There he met the mathematician V. January Garwick know and studied from 1945 finally even mathematics in Oslo where in 1956 he received his Candidatus - realium degree. The title of his thesis was Theoretical aspects of Monte Carlo methods. During his studies he completed in 1948 at Forsvarets forskningsinstitutt (FFI, Research Institute of the Norwegian armed forces) as an assistant by Jan V. Garwick full-time military service, where he was doing calculations for the building of Norway's first nuclear reactor and as head of the Computing Office Supervisor of Ole -Johan Dahl was. He remained there even after the conclusion and in 1957 Head of Operations Research. In 1959 he was co-founder of Norsk Operasjonsanalyseforening ( Norwegian Operations Research Club ) and stayed until 1964, its first chairman. In 1960 he transferred from the FFI to the Regnesentral Norsk ( NO, Norwegian Computing Center), where he was research director in 1962 with the task of establishing an institute for computer science, OR and Applied Mathematics.
Together with Ole -Johan Dahl, whom he brought to all 1963 NR, he developed for simulation purposes from 1961 to 1965, the first object-oriented language SIMULA, thus laying the foundation for the object-oriented programming ( OOP).
1974 Nygaard held lectures on computer science and society at the University of Oslo. He was a professor in Aarhus (1975 /76) and later received the appointment at the University of Oslo ( 1977-1996 ), where he managed the computer science committee from 1984 to 1985. In 1987 he was a visiting professor at Stanford University, and a visiting scientist at Xerox PARC and consultants of Apple's Advanced Technology Group. As the successor to Simula he developed with other programming languages delta and beta. In 1984 he left the NR, its member in 1996 but again. From 2001 he also worked for the newly founded Simula Research Laboratory.
The Norwegian king appointed him and Ole -Johan Dahl 2000 to commanders of the St. Olav's Order. In November 2001, he was honored for his role in the development of OOP along with Dahl only with the IEEE John von Neumann Medal, in February 2002 with the ACM Turing Award, the " Nobel Prize of computer science ".
He was also a member of the Norwegian Academy of Sciences and honorary member of the Object Management Group and has received honorary doctorates from the University of Lund and Aalborg Universitetscenter.
Nygaard was also active politically, it was the mid to late 1960 Board Member and Strategy Committee, Chairman of the left-wing party Venstre, later active in various committees of the Arbeiderpartiet, and in 1988 a leading member of the campaign Nei til EU, which should prevent Norway's accession to the European Union. Norway agreed in 1994 in a popular vote against accession to the EU. Nygaard promoted the IT expertise in trade unions, engaged in nature conservation organizations and represented Norway in information technology issues at the OECD. 1990 Nygaard received the Norbert Wiener Award for Social and Professional Responsibility.
From the marriage with his wife, Johanna (1951 ) had three children.
He died in Oslo at the age of 75 of a heart attack. A few weeks earlier, his friend and colleague Ole -Johan Dahl had died. The Association Internationale pour les Technologies Objets awards in her honor every year since 2005 the Dahl - Nygaard Prize.