Police responded after receiving reports of a man in the middle of Chassen Road in Flixton at 1.15am this morning.
The road was sealed off so the man could get treatment from paramedics and detectives could get to work to establish how the man ended up in the middle of a road with serious head injuries.
Train services were stopped at Chassen Road until the road was reopened.
A GMP spokesperson said: “We were called at 1.15am to a report for concern for welfare of a man on Chassen Road in Flixton.
“Officers attended and a man was found with serious head injuries in the middle of the road.
“He has been taken to hospital where he remains in a serious condition.”
If you saw anything or have information that could help police understand how this man ended up in the middle of the road you are asked to call police on 101 or call Crimestoppers anonymously on 0800 555 111.