The incident happened in Brighton Road near Old Lodge Lane just before 8.40am today (January 11).
Officers and London Ambulance Service crews attended and found a woman with multiple stab wounds.
She is currently in a stable condition but police are awaiting a full update from the hospital.
Urgent enquiries are on-going to locate a suspect.
A crime scene has been established, and will be in place for the remainder of the day.
A spokesperson for the Metropolitan Police said: “If anyone has any information about the incident, then please call 101 stating CAD1720/11Jan.
“You can also call Crimestoppers on 0800 555 111 to remain anonymous.”
