The girl, 19, was found dead at a property in Maidstone, Kent, just after 1.15pm yesterday.
A man, 27, who knew the dead girl, was arrested on suspicion of murder.
Kent Police said: “Detectives from the Kent and Essex Serious Crime Directorate have launched a murder investigation following a suspicious death in Maidstone.
“Kent Police and the South East Coast Ambulance Service attended a property in London Road following a call at 1.18pm on Tuesday 25 December 2018, where a 19-year-old woman was confirmed deceased.
“A 27-year old man from Maidstone was subsequently arrested on suspicion of murder and remains in custody.
“Both parties are believed to be known to each other.
“Enquiries to establish the full circumstances remain ongoing.”