Book excerpt: The introduction of harmful aquatic organisms to new environments by ships has been identified as a major threat to the world's oceans and to the conservation of biodiversity. Biofouling, described as the undesirable accumulation of microorganisms, plants, algae and animals on submerged structures (especially ships' hulls), is considered one of the main vectors for bioinvasions. These Guidelines for the control and management of ships' biofouling to minimize the transfer of invasive aquatic species are intended to provide a globally consistent approach to the management of biofouling. They were initially adopted by the Marine Environment Protection Committee (MEPC) of the International Maritime Organization at its sixty-second session, from 11 to 15 July 2011, in the form of resolution MEPC.207(62) following three years of consultation between IMO Member States, and subsequently revised following four years of consultation culminating in the adoption of the 2023 Biofouling Guidelines by the eightieth session of the MEPC, held from 3 to 7 July 2023. The Guidelines represent a decisive step towards minimizing the transfer of aquatic invasive species by ships.