Police said the Mercedes also hit two parked cars with no one inside. The driver, a man aged between his late 20s and early 30s, then got out of the luxury car and ran from bystanders along a nearby street. Police are looking for the man.
"Today, we've lost the life of a young girl who was just going about a Sunday morning bicycle ride," Inspector Stuart McGregor said.
"Unfortunately for her, the driver of the white Mercedes decided he was going to cut through on the left hand side of the other vehicles and at the same time he's collided with her and pushed her up against another car."
McGregor said the Mercedes was stolen in an aggravated robbery in Elsternwick last week.
He described the driver as "despicable".
"His first thought was to run," he said. "It wasn't to help, it wasn't to stop, it wasn't to think about the poor person he's hit."
The driver has been described as having shoulder-length hair, a dark beard and moustache, and was wearing black shoes and a black Adidas tracksuit.
"This is not going to go away ... we will not stop, we do not stop. We will arrest you," McGregor said.
"You're going to go to court; you're going to look a lot better if you come to us."
Shocked onlookers told the Herald Sun the driver calmly removed items from the back seat of the car before running off.
Local store worker Tony Christakakis described his shock of the horrific incident to the Herald Sun.
"I'm gobsmacked, dumbfounded, angry that someone could leave someone (for dead)," he said.
A passer-by rushed to perform CPR on the woman until paramedics arrived.
Police said they were still determining the exact circumstances of the collision and major crime detectives are investigating.
