The International Society for Horticultural Science (ISHS) is the world's leading independent organization of horticultural scientists. Its aim is "to promote and encourage research and education in all branches of horticultural science and to facilitate cooperation and knowledge transfer on a global scale through its symposia and congresses (International Horticultural Congress), publications and scientific structure." Membership is open to all interested researchers, educators, students and horticultural industry professionals.
The society dates from 1864, and was formally constituted in 1959. It is based in Leuven, Belgium, and is a founding member of the Global Horticultural Initiative. In 2008, it has over 7,000 members from about 150 countries.
The ISHS coordinates the distributed network of International Cultivar Registration Authorities, which are responsible for ensuring that the names of plant cultivars and cultivar groups are defined and not duplicated.