In recent years, several large outlet glaciers in Greenland lost their floating ice tongue, yet little is known regarding their stability over a longer timescale. Here we compile historical documents to demonstrate a major ice tongue collapse of Kangerlussuaq Glacier between 1932 and 1933. This event resulted in a 9-km retreat, exceeding any of the glacier's recent major retreat events. Sediment cores from the fjord are used to reconstruct sea surface temperatures and to investigate a potential sedimentological trace of the collapse. During the 1920s, local and regional sea surface temperatures and air temperatures increased rapidly, suggesting a climatic trigger for the collapse. Fjord bathymetry played an important role too, as the (partially) pinned ice tongue retreated off a submarine moraine during the event. This historical analogue of a glacier tongue collapse emphasizes the fragility of remaining ice tongues in North Greenland within a warming climate.