Dirk ter Haar was born at Oosterwolde in the province Friesland in the north of the Netherlands on 19 April 1919. He studied physics at the University of St Andrews in Scotland and Oxford University in England, obtaining an MA degree before carrying out postgraduate studies at Leiden University. In 1946 he was a research fellow of Niels Bohr at the Institute for Theoretical Physics in Copenhagen (now the Niels Bohr Institute), and received his PhD in Leiden in 1948 from Hendrik Kramers for a dissertation on the origin of the Solar System. From 1947 to 1950 he was a visiting associate professor of physics at Purdue University.
In 1950 he obtained a post as professor of physics at the University of St. Andrews, and later became a British citizen. In 1952 he was elected a Fellow of the Royal Society of Edinburgh. His proposers were Jack Allen, David Jack, Daniel Edwin Rutherford and Edward Thomas Copson.
Many prominent scientists studied under Ter Haar, including Anthony Leggett, winner of the Nobel Prize in Physics in 2003, and Deng Jiaxian, one of the leading scientists and founders of Chinese nuclear weapons programs.
Dirk could read Russian, and played a prominent role in disseminating the works of Soviet physicists such as Landau and Kapitsa to the western world. He also translated the classic monograph Quantum Mechanics by Alexander Davydov into English.
He retired from his positions at Oxford in 1986, and died at Drachten in the northern Netherlands on 3 September 2002.
In 1949 Dirk ter Haar married Christine Janet Lound and together they had two sons and a daughter. His daughter, Gail ter Haar, became a reader in physics as well, specializing in therapeutic ultrasound.
He wrote numerous books on physics, such as Elements of Statistical Mechanics (1954). In addition, he wrote a book on Kramers and was a founding editor for Physics Letters (1962) (later Physics Letters A) and Physics Reports (1971). In 1984 the book Essays in Theoretical Physics in honour of Dirk ter Haar was published in honour of his work in statistical physics and quantum mechanics.