It is believed the 47-year-old UDA man was fatally wounded with a Samurai sword during a fight
Another man, aged 52, is in a critical condition in hospital after the attack in south Belfast.
It happened in Kirkistown Walk in the Belvoir Estate.
The ambulance service said it received a call to attend the Belvoir Estate at 8.20 pm on Wednesday night.
One man, aged 46, has been arrested.
Detective Chief Inspector Richard Campbell has appealed for information.