Galaxias fontanus, the Swan galaxias, is a species of fish in the family Galaxiidae. It is endemic to eastern Tasmania, Australia.

The brownish-olive fish is only found in the trout-free headwaters of the Swan and Macquarie River catchments. The streams occupied by the species have a low gradient and shallow waters. Natural populations are very small and fragmented, however the species has been successfully introduced into other predator-free streams.

The fish ranges from 7cm to 13cm and can weigh up to 8 grams. Swan galaxias are carnivores and feed on aquatic and terrestrial insects. The fish have a spawning period is an extended period of time of 3 months within the spring season (typically August and October). The number of eggs that the Swan galaxias lay range from 150 to 550 eggs and have a diameter between 2.2 and 2.5mm.

It is listed as Endangered on the IUCN Red List and Environment Protection and Biodiversity Conservation Act 1999. The primary threat to the Swan galaxias is predation from exotic and introduced species, poor water quality, extreme climatic conditions and human activities such as agriculture and damming. Conservation practices were funded by the World Wide Fund for Nature (WWFN) and the Endangered Species Program of Environment Australia (ESP) to conserve the species population.

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