A 14-year-old girl and a 12-year old girl were in collision with a car on Normanton Hill, the B6064.
Jasmyn Chan suffered fatal injuries and sadly died.
The car, thought to be small and dark-coloured, and possibly a Volkswagen or a Honda, was travelling downhill towards the A57 Mosborough Parkway. The driver of the car failed to stop at the scene of the collision.
Officers are appealing for the driver of the car to come forward and contact South Yorkshire Police.
The car is likely to have some visible signs of damage from the collision.
Ch Insp Stuart Walne said: “Jasmyn was a very active girl, very friendly, a very giving person, and unfortunately her life’s been taken away in this collision.
“This is a tragic situation that has taken a young life and seriously affected another.
“If you were the driver of this car, please contact police immediately.
“There may have been reasons that you didn’t stop last night, but now a girl has died and we need to speak to you.”
Police are also urging anyone who witnessed the collision or saw the small dark car in the Normanton area or anyone who may have any information, to please call 101 quoting incident number 1098 of 9 May 2014.
Alternatively call Crimestoppers anonymously on 0800 555 111