Police believe 14-year-old Samuel Berkley was involved in a collision with a car and say he sustained "unsurvivable" injuries.
Samuel was discovered on the hard shoulder of the M67 eastbound at junction 3 in Hyde, Greater Manchester, during the Friday afternoon rush hour.
He was taken to hospital where he died early on Saturday.
A grey convertible BMW, which had been travelling eastbound and stopped at the scene, was involved in the collision.
In a statement, police said the teenager was a talented footballer who had recently started playing for Hattersley FC.
He attended Audenshaw school in his local area and had recently become an uncle to his older brother's new baby.
His family said they were heartbroken and hoped everyone would remember Sam for the fun, outgoing and friendly boy he will always be.
Sergeant Lee Westhead said: "My thoughts are with the victim's family who are being looked after by specially trained officers at this difficult time.
"Whilst we work to uncover how this has happened and piece together the moments before the collision, I am asking the public to help in any way that they can.
"If you were in the area at approximately 5.25pm on December 1 and saw a pedestrian on the motorway, or have dashcam images, please get in touch and share this information."
Anyone with information is asked to call Greater Manchester Police's serious collision investigation unit on 0161 856 4741.