Gardaí were called to the scene of an incident in a house at Connolly Street in Sligo Town at around half past one this afternoon.
A 20 year-old man, who investigating Gardaí believe was the victim of an assault, was pronounced dead at the scene.
The office of the state pathologist has been notified and a Garda technical team are currently at the scene.
A 31-year-old man was arrested a short time later in connection with the investigation and is currently detained at Ballymote Garda Station.
Gardaí are appealing to anyone who may have witnessed the assault or anyone with information to contact Sligo Garda Station the Garda Confidential line or any Garda Station.
Investigations are continuing.
