Lake Moondarra is an impounded reservoir formed by the Leichhardt River Dam, a concrete-faced rock-filled embankment dam across the Leichhardt River, located near Mount Isa in north-west Queensland, Australia. The dam was built in 1958 for the supply of potable water to the town of Mount Isa, upstream, and water supply for the adjacent Mount Isa Mines (MIM) mining lease. Lake Moondarra is used for recreation purposes and includes picnic areas, pontoons, a ski jump, and water sports facilities. The lake is popular with birdwatchers, sailors and anglers.
Prior to the construction of the dam, the area was the location for one of Australia's largest stone axe quarries. The axes were traded amongst Indigenous Australians across distances up to .
Construction of the Leichhardt River Dam began in 1956, was completed on 6 November 1958, and cost Aã1.7 million. The dam was built for MIM and, at the time, was the largest water scheme in Australia financed by private enterprise. The original construction was started by the American Utah Construction Company and Thiess Brothers completed the project.
The dam is high, long, and holds back when at full capacity. The impounded reservoir covers and draws from a catchment area of . In 1971, the uncontrolled spillway was raised to its present height of .
On 20 October 1962, the reservoir was officially gazetted as Lake Moondarra after a 1961 competition was won by a Mount Isa local, Danny Driscoll. The Aboriginal word moondarra means "plenty of rain" and also "thunder".
Transport Bay is a man-made beach on the lake, so named because sand was deposited on the banks of the lake by MIM Holdings' trucks.
The dam is stocked with approximately 10,000 fingerlings annually for recreational fishing. It is stocked with barramundi and sooty grunter. 22 different freshwater species inhabit the dam.
The Lake Moondarra Fishing Classic was inaugurated in 1999.
In 1984, a species of weevil was successfully used as a biological pest control to contain a proliferation of the weed Salvinia molesta in the lake. The first releases were made in 1980 and the weevil destroyed tens of thousands of tonnes of weed.