Marc Van Montagu (born 10 November 1933 in Ghent) is a Belgian molecular biologist. He was full professor and director of the Laboratory of Genetics at the faculty of Sciences at Ghent University (Belgium) and scientific director of the Genetics Department of the Flanders Interuniversity Institute for Biotechnology (VIB). Together with Jozef Schell he founded the biotech company Plant Genetic Systems Inc. (Belgium) in 1982, of which he was Scientific Director and member of the board of Directors. Van Montagu was also involved in founding the biotech company CropDesign, of which he was a Board member from 1998 to 2004. He is president of the European Federation of Biotechnology (EFB) and of the Public Research and Regulation Initiative (PRRI).
Van Montagu and his colleagues were credited with the discovery of the Ti plasmid. They described the gene transfer mechanism between Agrobacterium and plants, which resulted in the development of methods to alter Agrobacterium into an efficient delivery system for gene engineering and to create transgenic plants. They developed plant molecular genetics, in particular molecular mechanisms for cell proliferation and differentiation and response to abiotic stresses (high light, ozone, cold, salt and drought) and constructed transgenic crops (tobacco, rape seed, corn) resistant to insect pest and tolerant to novel herbicides. His work with poplar trees resulted in engineering of trees with improved pulping qualities.