It is understood the women, aged 58 and 22, were from the same family.
They were fatally injured when their car was in collision with another car about three miles from Fermoy on the Ballyduff Road.
The driver of the other car was not seriously injured. The collision happened shortly before 11:40 local time on Tuesday.
It is believed the car was leaving a junction when it was struck from the side and went into a ditch and then into a stream.
Two women have died following a car crash in County Cork in the Republic of Ireland.