Book excerpt: The Polar and Subpolar region comprise one of the seven regions in the world, from the Arctic to the Antarctic, the Atlantic, Pacific, and Indian Oceans. Marine biodiversity in the polar and subpolar regions is one of the richest on earth, hosting important populations of crustaceans, pelagic and benthic species that provide resources for the many seabirds and marine mammals that congregate there. However, these ecosystems, as well as their biodiversity, are vulnerable and already affected by the impacts of climate change and other threats. The high climatic dynamics in those areas have already generated strong modifications to the environment, with irreversible losses in biodiversity and diminished ecosystem services that are essential for the whole planet. The current need to study and understand the biodiversity of the world's oceans makes polar and sub-polar areas key regions for taxonomic and ecological studies.