Lake Edgar was a natural fault scarp pond on the upper reaches of the Huon River in South West Tasmania.

Lake Edgar was actually two small lakes that were created when the Edgar fault caused the plains below Mount Anne, on the upper reaches of the Huon River, to move upwards by little more than 6 metres (20 ft), causing the river to dam and divert northwards around Scotts Peak.

The two Quaternary ruptures each elevated the western side by 2.5 metres (8 ft 2 in).

The fault separated graphitic phyllite in the east from metasiltstone, argillite, quartz sandstone conglomerate on the west.

The fault possibly continues through weak talc containing ultrabasic rocks and into the Gell River Fault about 30 kilometres (19 mi) north, which has an older Late Pleistocene displacement.