Police are investigating a collision between a car and a motorcycle in Yarrambat on Sunday afternoon (May 31).

It is understood that a red 1990 Honda motorcycle was travelling south on Yan Yean Rd when it collided with a white 2018 Mercedes station wagon about 3.05pm.

The motorcyclist, a 54-year-old Briar Hill man, sustained life-threatening injuries and was transported to hospital.

The driver, a 31-year-old Doreen man, stopped at the scene to assist and rendered first aid.

Investigators have spoken with several people who were in the area at the time and witnessed the collision.

The investigation remains ongoing.

Anyone with information is asked to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au