Piet Borst CBE (born 5 July 1934, in Amsterdam) is emeritus professor of clinical biochemistry and molecular biology at the University of Amsterdam (UVA), and until 1999 director of research and chairman of the board of directors of the Netherlands Cancer Institute and the Antoni van Leeuwenhoekziekenhuis (NKI-AVL).
He received his PhD for an investigation of tumor mitochondria (Supervisor Edward Slater).
In 1983 Borst moved to the Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital where he became director of research and in 1987 also chairman.
After his mandatory retirement in 1999, Borst became a staff member and continued running his lab, studying mechanisms of chemotherapy resistance in cancer cells, the physiological functions of drug transporters and the biosynthesis and function of DNA Base J, a new base in DNA that had been discovered in trypanosomes by his research group.
Borst contributed to discussions about science and science policy in the Netherlands: In the seventies he was spokesman for science in the rather virulent discussions on recombinant-DNA experiments; as a director of the cancer institute he regularly reported on advances in cancer research/treatment in the press and on radio/TV; he was a member of the Innovation Platform, a small thinktank of the Dutch prime-minister; and for 23 years he wrote a monthly column in the prime intellectual daily, the NRC Handelsblad.