Ireland’s marine waters host a rich and diverse range of species and habitats, including important fish spawning and nursery areas. Ecosystems provide a series of services for human well-being (ecosystem services) either directly (as food and fibre) or indirectly by providing clean air and water. Biodiversity plays a key role in the functioning of ecosystems and their ability to provide ecosystem services. The value of biodiversity and benefits from ecosystem services reach far beyond that which can be measured in financial terms. Evidence from monitoring of natural habitats and species in Ireland’s marine environment indicates that many habitats are not in good condition. Protecting and improving the condition of marine habitats and ecosystems is a challenge for all users of the sea.