Lake Flannigan is a natural freshwater lake on King Island, Tasmania, Australia, situated four kilometres south of the Cape Wickham Lighthouse, in the northern locality of Wickham.
At approximately 150 hectares, it is the largest body of water on King Island. The size of the lake fluctuates significantly. In times of sustained high rainfall the length can reach almost 2 kilometres, and its width in some parts can be up to 1.5 kilometres.
The floor of the lake lies 15.25 metres. AHD. Reports of the depth of the water vary widely from 9.1 metres in 1887 to 2 metres in 2007 after a period of severe drought coupled with the previous mis-direction of drainage into the lake.
