A 370 million-year-old fish fossil will join the kookaburra, platypus, blue groper and black opal on the list of NSW state emblems.
With the scientific name, Mandageria fairfaxi, after a local creek and publisher James Fairfax, the fish fossil is one of the largest in the world, measuring up to 1.7 metres in length.
The fossil was found during a 1993 excavation near Canowindra in the NSW central west, which has become a tourist hotspot for paleontology enthusiasts in the world, according to the government.
"By raising awareness of fossils and the state's unique geological history, geotourism across regional NSW will be boosted," said member for Orange Andrew Gee on Thursday.
NSW joins Western Australia as the only other Australian state or territory to have a state fossil emblem.
"This declaration recognises the rich scientific heritage that lies beneath our feet," Resources Minister Anthony Roberts said.
A competition to nickname the fossil is open for all NSW primary school children and will close on September 18.