The man in his 20s who had been detained at Claremorris Garda station in relation to the death of Joseph Deacy in Swinford has been released without charge last night.
Gardaí said a file will be prepared for the Director of Public Prosecutions.
Joseph Deacy (21), from St Albans in Hertfordshire, England, was staying at a house in Derrynasillagh, Swinford, while in Ireland for a two-week holiday.
Mr Deacy had returned to the house in the early hours of Saturday, August 12th, following a night out in Kiltimagh.
At about 6am, a passerby noticed him in a collapsed state outside the property with visible injuries. He had sustained a trauma injury to the head but was still alive.
He received attention from paramedics at the scene and was taken to Mayo University Hospital. However, he died the next day after being transferred to Beaumont Hospital in Dublin, which specialises in treating head injuries.