The investigation for missing woman Tina Satchwell has been upgraded to a murder inquiry.
The 45-year-old has been missing from her home on Grattan Street in Youghal, Co Cork since March 2017.
A man aged in his 50s was arrested on Tuesday afternoon on suspicion of murder.
He is being detained under Section 4 Criminal Justice Act at a Garda station in Cork.
Gardaí have also sealed off a house on Grattan Street in Youghal for a technical examination.
A Family Liaison Officer has been appointed to the family of Ms Satchwell.
Gardaí are contining to appeal for any person who may have information relevant to the investigation to contact Midleton Garda station on 021-462-1550, the Garda Confidential Line at 1800-666-111 or any Garda station.
