Southport Lagoon is a rural locality in the local government area (LGA) of Huon Valley in the South-east LGA region of Tasmania. The locality is about south of the town of Huonville. The 2016 census recorded a population of nil for the state suburb of Southport Lagoon.
Southport Lagoon is a confirmed locality.
The waters of the Tasman Sea form the eastern and southern boundaries. Southport Lagoon, the body of water, is contained within the locality.
Route C636 (South Cape Road) passes to the west.