Two men are unaccounted for after a car crashed into a river north-west of Sydney overnight.

At about 11.50pm, emergency services were called to the Macdonald River at St Albans, about 20km north of Wisemans Ferry.

They were told a car had crashed into the river before one man, a passenger, managed to escape and reach the riverbank.

The man, aged in his 20s, was assessed by paramedics but did not require any further treatment.

Police were told two other men were in the car at the time but have not been found.

The SES and firefighters have begun a search for them.

Anybody with information is urged to contact Hawkesbury Police, or Crime Stoppers on 1800 333 000.

DOWNLOAD THE 9NEWS APP : Stay across all the latest in breaking news, sport, politics and the weather via our

See Full Page