The 21-year-old was found with multiple wounds in Church Gardens, South Ealing around 12.10am on Tuesday after police were called to reports of a stabbing.
Officers attended along with paramedics and London’s air ambulance.
Scotland Yard said the victim had a number of stab injuries and despite the best efforts of emergency services, she was pronounced dead at the scene.
A 20-year-old man has been arrested on suspicion of murder and taken into custody at a west London police station.
Officers are confident they know the woman’s identity and are in the process of informing her next of kin.
A post-mortem examination will be arranged in due course.
A crime scene remains in place and enquiries continue.
Anyone with information about the incident is asked to call police on 101, quoting CAD 77/17May, or Crimestoppers anonymously on 0800 555 111.