AbstractWe present results of analysis of lightning observations and satellite measurements of ionospheric magnetic field fluctuations in the ultralow frequency (ULF) range. The fluctuations are measured by Swarm satellites, while the lightning observations are provided by the Geostationary Lightning Mapper (GLM) and the World ELF Radiolocation Array (WERA). We identify spatio‐temporal relationships that demonstrate a leakage of electromagnetic fluctuations caused by lightning into the upper ionosphere. Causal association between the two phenomena is evidenced by investigating relations between lightning and fluctuation properties. The presented results suggest that lightning generate ULF fluctuations in the ionosphere that can be detected by satellites, if the lightning‐satellite geographic distance is less than ∼5°. Typical properties of the fluctuations caused by lightning are described in the paper. To our knowledge, this is the first direct experimental confirmation of a link between lightning and magnetic field fluctuations in the upper ionosphere in the ULF range.