A man who was apparently lying on a highway in southern NSW has been hit by a car and killed.

A 51-year-old Coolamon woman was driving on the Olympic Highway thorough Culcairn, about 50km north of Albury, at 1.30am (AEDT) Saturday when she "struck something", police said.

Police were called, and officers found the body of 33-year-old Daniel Hansen on the highway.

"Police attended the location after it was discovered a man was deceased after apparently lying on the roadway," police said in a statement.

A report was being prepared for the coroner.

Later on Saturday, a cyclist was killed when he was hit by a four-wheel drive on a motorway in Sydney's west.

The fatal crash occurred just after 7.30 am (AEDT) on the eastbound lane of the M4 at Emu Plains, a police spokesman told AAP.