The body was found at a property in the Victoria Street area of Lurgan on Sunday afternoon.
Detective Inspector Darren McCartney of MIT said: “Police received the report of the death shortly after 2.15pm this afternoon.
“A 45 year old man has been arrested at the scene on suspicion of murder and he remains in police custody at this time.
“I am appealing for anyone with any information that can assist with the investigation to contact detectives in Lurgan on 101 quoting reference number 769 of 06/08/17.
“Information can also be passed anonymously via the independent charity Crimestoppers on 0800 555 111.”