Lake Ewlyamartup is an ephemeral salt lake in the Great Southern region of Western Australia located approximately 17 km (11 mi) east of the town of Katanning and about 294 km (183 mi) south east of Perth, in the locality of Ewlyamartup.

The landscape is a mixture of saline and fresh lakes and swamps with lunettes, dunes and swales on aeolian and lacustrine deposits and alluvium over granite based rocks.

[5] A sacred site is situated on the lakes outskirts and was once an Indigenous camp ground hundreds of years ago.

In 2010 the local community removed 20,000 m3 (710,000 cu ft) of nutrient rich sludge from the lake and planted 100,000 trees in the catchment area.

At times when the water levels are high enough it is used for canoeing, kayaking, sailing, swimming, water-skiing and windsurfing.

[10] The area is part of the Dumbleyung Vegetation System, which is mostly gently undulating with scattered cappings of laterite in the north with salt-flats and lakes found in the larger valleys often with sand deposits.