The Patagonian Ice Sheet was a large ice sheet that covered all of Chile south of approximately present-day Puerto Montt during the Last Glacial Maximum. Some maps have the Patagonian Ice Sheet connected to the icecaps of the Altiplano by continuous glaciers all the way through Chile.

The ice sheet extended beyond the crest of the Andes into Argentina, but because of the dryness of the climate it did not reach beyond present-day lakes such as the Yagagtoo, Musters, and Colhue Huapi. At its peak, the Patagonian Ice Sheet covered about 480,000 square kilometres of land, of which about 4 percent remains glaciated today. However, during the first Pleistocene glacial period, a vast ice sheet extended to the Atlantic Ocean, probably eroding large areas of land in Argentina. Large fjords occupy deglaciated land, whilst large numbers of islands, the best-known of which is Chiloé have been carved out.

Unlike the Laurentide Ice Sheet or the ice sheets of Northern Europe, the Patagonian Ice Sheet did not cause major extinctions or loss of biodiversity. This is because the flora remaining to the north of the ice was isolated by the Atacama Desert and was able to speciate easily whereever suitable microclimates occurred. In fact, most of the original Antarctic flora survives today on land occurpied by the ice sheet.

See also

• Ice sheet
• Magellanic subpolar forests
• Valdivian temperate rain forests
• Geography of Argentina
• Geography of Chile