Officers were called to an “incident” at a property in Clydebank, West Dunbartonshire, at about 3.50am.
A man aged 38 was pronounced dead at the scene in the Singer Street property.
A 34-year-old woman has been arrested in connection with the incident and is due to appear at Dumbarton Sheriff Court on Monday.
Police Scotland are urging anyone with information to get in touch.
Detective Inspector Erin Renwick, of the major investigation team, said: “A police presence will remain in the area for the time being to allow enquiries to be carried out.
“This incident is now being treated as murder.
“Although this happened in the early hours of the morning, I would urge that if you have any information surrounding this incident to get in contact with officers.
“Police Scotland can be contacted on 101 quoting incident number 0719 of Friday, June 26, 2020, or Crimestoppers anonymously on 0800 555 111.”
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