A passenger was killed and a driver left in critical condition after a single-vehicle crash on Sunday.

The two men in their 30s were travelling on Carlisle Ave at Hebersham, in Sydney’s west, when their car hit a tree at about 12.25am.

Emergency services arrived to discover the passenger had died at the scene, NSW Police said.

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He is yet to be formally identified.

The driver was taken to Westmead Hospital, fighting for life.

A report will be prepared for the coroner.

Investigations are ongoing and anyone with information is urged to contact Crime Stoppers.