A young child who went missing from Southern Cross Station last night has been found safe and well.

The boy, 12, was with a family member waiting for a train to Bendigo from Southern Cross station, but the 5.55pm train departed before he boarded.

Police say the child, who has autism, left the station by the time his family member was able to return to the platform.

They made a public appeal for information this morning, also releasing an image in the hope someone recognises him.

He was discovered safe and well shortly before 8am on Thursday.