You are most cordially invited to the 21 International Seaweed Symposium which will be held in Bali, Indonesia, April 21-26, 2013. The theme of the 21 International Seaweed Symposium is “Seaweed Science for Sustainable Prosperity”. The International Seaweed Symposium (ISS) is held every three years under the auspices of the International Seaweed Association (ISA). For more than six decades it has been the foremost international symposium for individuals and organizations involved with seaweed research and utilization. Scientific research plays a fundamental role in developing seaweed cultivation and seaweed industries. The ISS provides a forum for scientists, technologists, business people and resource managers to present their latest research results, exchange ideas and develop new synergies. The 21 International Seaweed Symposium is being held in Bali, Indonesia in the heart of the Coral Triangle where seaweed farming employs tens of thousands of coastal people in family enterprises. Seaweed utilization in the Coral Triangle has developed primarily in response to raw material demands of the carrageenan and agar industries. There is vast potential for expansion and diversification of seaweed production and utilization in the region including development of seaweeds as components of integrated multi-trophic aquaculture (IMTA) systems. There is a clear and present need for expanded scientific research and development to enable economically and environmentally sustainable seaweed industry development not only in the Coral Triangle but also in other coastal regions throughout the world. It is a goal of the 21 International Seaweed Symposium to catalyze support for such scientific activities.