<p>Glacial outburst floods (j&#246;kulhlaups) have occurred across Earth throughout the Quaternary, often leaving a geomorphologic, sedimentological, and climatic legacy that extends far beyond the source region and can persist for millennia. Furthermore, they pose an increasing geohazard in glaciated landscapes worldwide due to climate-driven ice retreat. Iceland experiences more frequent j&#246;kulhlaups than nearly anywhere on Earth, though most research focuses on floods triggered by subglacial volcanic and geothermal activity. However, abundant evidence also exists for non-volcanogenic floods from proglacial lakes, which may serve as a better analogue for most global j&#246;kulhlaups.</p><p>As the Icelandic Ice Sheet retreated across Iceland in the Late Pleistocene-Early Holocene, meltwater lakes formed at ice margins and periodically drained in j&#246;kulhlaups. Some of the most catastrophic floods drained from ice-dammed Glacial Lake Kj&#246;lur, surging across southwestern Iceland from the interior highlands to the Atlantic Ocean. These floods left extensive geomorphologic evidence along the modern-day course of the Hv&#237;t&#225; River, including canyon systems, scoured bedrock, boulder deposits, and Gullfoss&#8212;Iceland&#8217;s most famous waterfall. The largest events reached an estimated peak discharge on the order of 10<sup>5 </sup>m<sup>3</sup> s<sup>-1</sup>, ranking them among the largest known floods in Iceland and on Earth. Yet, all our evidence for the Kj&#246;lur j&#246;kulhlaups comes from only one publication from a quarter-century ago.</p><p>This project employs a combination of field, modelling, and laboratory methods to better constrain flood timing and dynamics at this underexplored site. This talk synthesizes geomorphologic field mapping, HEC-RAS hydraulic simulations and paleohydraulic calculations, and cosmogenic nuclide exposure dates to reconstruct Kj&#246;lur j&#246;kulhlaup routing, hydrology, and chronology. It situates these events within the context of Pleistocene-Holocene Icelandic Ice Sheet retreat and paleoenvironmental change, presenting a series of scenarios of ice margin position, glacial lake extent, and j&#246;kulhlaup drainage. Finally, it assesses the Kj&#246;lur j&#246;kulhlaups as an analogue to contemporary glacial outburst floods in other Arctic and alpine regions in terms of flood frequency, dynamics, and landscape impact.</p>