The Maroochy River is a river in South East Queensland, Australia. The river rises from the eastern slopes of the Blackall Range and flows east through Eumundi, before entering the sea at Cotton Tree, Maroochydore. Other populated centres in the catchment include Nambour, Eudlo, Yandina and Coolum.
The watershed of the Maroochy River encompasses 630 square kilometres (240 sq mi) of undulating hills which have been cleared for agriculture and urban uses. There are three dams in the catchment area including Wappa Dam, Cooloolabin Dam and Poona Dam which total to 27,997 megalitres (988.7×106 cu ft) of capacity.
There are two main arms: North and South Maroochy Rivers. Tributaries of the river include Petrie Creek and its major tributary Paynter Creek, Eudlo Creek, Coolum Creek, Doonan Creek and Yandina Creek.
Significant floods on the Maroochy River have occurred in 1893, 1951, 1974 and 1992. In 1994 the Maroochy River flood warning system was set up to provide river height predictions for the Maroochy Shire Council.
There are a number of named Islands in the river including Pincushion Island, Goat Island, Channel Island, Chambers Island & Bungee’s Island.
The mouth of the river was affected by the 2009 southeast Queensland oil spill, reaching about 2 kilometres (1.2 mi) upstream to the Maroochy Bridge.