An elderly woman is fighting for her life after being stabbed in the driveway of a home in Melbourne's north today.

Police said a 31-year-old Alphington man was arrested after the woman was stabbed in Yerrawa Drive, Watsonia, around 12.30pm.

He was arrested in the backyard of a home in Henry Street.

Police said the woman, aged in her early 70s, has been flown to The Alfred hospital in a life-threatening condition.

Police are urging anyone with information about the stabbing to contact Crime Stoppers on 1800 333 000 or www.crimestoppers.com.au.