A teenager who was stabbed by his relative as he walked off a Fremantle bus has died in hospital.

The 18-year-old man died at the weekend after being allegedly stabbed in the chest by his relative, Tanya Ugle, on Wednesday.

A man has died in hospital after he was allegedly stabbed while walking off a bus in Fremantle. (File pic)

A police spokesman on Thursday alleged the pair boarded a bus at Fremantle Train Station around 2.15pm, but the bus driver stopped the bus shortly after departing the station due to the conduct of the woman.

The 35-year-old woman was then asked to exit the bus.