The inicident happened in Moneymore last night, Friday 9 March.
The 22 year old was found slumped inside a vehicle on the Carndaisy Road by a passer-by at around 9.50pm.
Police and paramedics were called and the male was found to have sustained a significant head wound.
He was taken to hospital where he remains this morning undergoing treatment.
Inspector Gregory Smyth said: “We are working to establish precisely what has happened and how this man sustained his injury.
“We are keen to hear from witnesses or anyone with information. Officers can be contacted by calling 101, quoting reference number 1484 09/03/18.”