This dataset shows the modelled distribution of sei whales (Balaenoptera borealis). AquaMaps (www.aquamaps.org) is a species distribution modelling approach that provides standardised range maps for marine species using available information on species occurrence. IUCN status: Endangered (Red List of Threatened Species). The modelled distribution was generated using the AquaMaps online species distribution model. Methodological notes (provided by K. Kaschner) are also available. Observed occurrence records (663 cells; FAO areas: 18, 21, 27, 31, 34, 37, 41, 47, 48, 51, 57, 58, 61, 67, 71, 77, 81) were obtained (August 2013) from the Global Biodiversity Information Facility (GBIF; www.gbif.org). These were supplemented by additional information obtained through online species databases such as FishBase (www.fishbase.org) and SeaLifeBase (www.Sealifebase.org), as well as published information on species-specific habitat usage and expert knowledge. The distribution model was based on five environmental variables (depth, temperature, salinity, primary production, and sea ice concentration), and details of the species envelope are in the dataset-specific information (provided by K. Kaschner).