The leaks from the Nord Stream gas pipelines in September 2022 released a large amount of methane (CH₄) into the atmosphere. We provide observational data from a satellite instrument that shows a large CH₄ plume over the North Sea off the coast of Scandinavia. We use this together with atmospheric models to quantify the CH₄ leaked into the atmosphere from the pipelines. We find that 219–427 Gg CH₄ was emitted, making this the largest individual fossil-fuel-related CH₄ leak on record.