A homicide inquiry has been launched after a man was fatally stabbed in Invercargill overnight.

Police said they received a report at about 12.45am that two men were injured near the Invercargill District Court on Don Street.

One man with stab wounds was found to be unconscious and he died at the scene.

Another man, also with stab wounds, had critical injuries and was taken to hospital where he has now undergone surgery.

He is still in a critical condition, police said.

Police placed a guard at Don Street overnight and said the scene investigation would continue today.

Cordons are in place on Don Street between Kelvin Street and Dee Street.

Police want to speak to anyone who was either walking or driving through the vicinity of Don Street at the time.

Anyone with information can contact police on 105 and quote event number P050337575 or provide information anonymously via Crime Stoppers on 0800 555 111.