Gardaí arrested a woman in her 30s, the force said on Sunday, following the discovery of a body in Navan, Co Meath.
The man (40s) was found at a residential property on Academy Street on Saturday.
The arrested woman is being held at Kells Garda station, detained under Section 4 of the Criminal Justice Act 1984.
The body of the dead man were preserved and remain at the scene for forensic and technical examination. The State Pathologist and local coroner were notified of the death.
The investigation is on-going.
Investigating gardaí are appealing for witnesses to come forward. Anyone with information is asked to contact the incident room at Navan Garda Station 046-9036100 or the Garda Confidential Line 1800 666 111.
On Saturday, it was reported that a body had been discovered in "unexplained circumstances" elsewhere in the county, in Ashbourne.
