The International Association of Classification Societies (IACS) is a technically based non-governmental organization that currently consists of twelve member marine classification societies. More than 90% of the world's cargo-carrying ships’ tonnage is covered by the classification standards set by member societies of IACS. 

Marine classification is a system for promoting the safety of life, property and the environment primarily through the establishment and verification of compliance with technical and engineering standards for the design, construction and life-cycle maintenance of ships, offshore units and other marine-related facilities. These standards are contained in rules established by each Society. IACS provides a forum within which the member societies can discuss, research, and adopt technical criteria that enhance maritime safety.

Croatian Register of Shipping was associated member of International Association of Classification Societies from April 1973 till 2004, and from May 2011 CRS gained the status of IACS Member.