How animals navigate during long-distance migration remains a mystery. Many theories have been proposed1 (Keeton, 1979), with the Earth’s magnetic field emerging as a clear potential source of orientational information for navigational decision-making across diverse taxa2 (Putman, 2022). Yet, the mechanics involved in magnetic navigation remain unknown3 (Schneider et al., 2023). Globally distributed records available from historic whaling4-5 (AOWLD, 2023; Yablokov et al., 1998) in combination with modern satellite-tracking datasets6 (Horton et al., 2022) for baleen whales create a unique opportunity to illuminate the mechanics of cetacean navigation. Here, we show that baleen whale migratory destinations over the last >200 years are systematically distributed in horizontal plane magnetic coordinates. Specifically, blue (Balaenoptera musculus), bowhead (Balaena mysticetus), fin (Balaenoptera physalus), gray (Eschrichtius robustus), humpback (Megaptera novaeangliae), and right (Eubalaena spp.) whales non-randomly inhabit areas where magnetic declination (MD) closely approximates integer and half-integer multiples of the Earth’s 23.44° axial tilt. Our findings, which are highly reproducible through both space and time, demonstrate that baleen whale navigation between seasonal habitats occurs via the integration of magnetic and astronomic orientation cues3. By referencing MD values to the rise and set azimuths of the Sun, baleen whale movements define mechanistic horizontal plane heliomagnetic coordinate trajectories across all ocean basins.