The Antarctic krill is a dominant species of the Southern Ocean ecosystem, with possibly the largest biomass of any wild animal species on Earth. Krill play fundamental roles in marine food webs, including carbon cycling, and nutrient cycles. They are also the target for the largest fishery by tonnage caught in the Southern Ocean. The best estimate of circumpolar krill biomass is 379 million tonnes, but at regional scales krill biomass is highly variable from year to year. A krill abundance decline has been reported between the 1970s and the 2010s at the northern edge of krill habitat in the Atlantic sector. Farther south, summer seawater temperature remained below krill’s upper thermal limit, and abundance remained stable. Multiple analyses suggest a southward contraction of krill distribution in the southwest Atlantic. The krill fishery is managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR.org). The total fishery catch and the spatial concentration of that catch has been increasing due to recent technological advancement and commercial interest. New technology and coordination between scientists and the fishing industry can advance understanding of krill, particularly during winter and beneath sea ice. Sustained research support is important for improving management of the krill fishery under climate change.