Kumpupintil Lake, formerly known as Lake Disappointment, is an endorheic salt lake situated in the Little Sandy Desert of Western Australia, approximately 300 kilometres east of Newman. The lake is large in extent — roughly 160 kilometres long with a surface area of around 330 square kilometres — and sits at an elevation of 325 metres above sea level. Despite its size, it is not a viable paddling destination under normal circumstances.

The lake is ephemeral, meaning it is dry the vast majority of the time. Water accumulates only during very wet periods, and even then the lake retains all inflow with no outflow, resulting in extremely high salinity. The water is not drinkable and the salt concentration is visibly evident around the lake's edges. When water is present, variations in depth and salinity produce distinct colour differences across the lake's surface.

The surrounding landscape is arid desert, on the edge of the Gibson Desert, with sand dunes encircling much of the lake. The area is one of the most remote in Australia, with no significant population centres nearby and limited infrastructure. Karlamilyi National Park, Western Australia's largest and most remote national park, lies to the north of the lake. The region does support water birds when the lake holds water.

The lake holds cultural significance for the Western Desert Martu people, whose name for it — Kumpupintil — became the official gazetted name in November 2020, replacing the colonial name given by explorer Frank Hann in 1897. Hann named it after following inland-flowing creeks in the east Pilbara region, expecting to find a freshwater source, only to discover a salt lake.

Mean maximum temperatures in the area exceed 40°C in summer months (December through February), with mean minimums remaining above 25°C during those months. Rainfall is sparse and irregular, with the highest averages occurring in February. Anyone travelling to this area should be prepared for extreme heat, extreme remoteness, and the strong likelihood that the lake will be completely dry upon arrival.