The two incidents occurred late Thursday and early on Friday in Sydney's southwest, NSW Police said.

An 80-year-old man died after being hit by a car on Oxley Street in Campbelltown about 11.15pm on Thursday.

Paramedics attended and treated the man, but he died at the scene and is yet to be formally identified.

The 26-year-old driver was not injured but he was taken to hospital for mandatory testing.

A report is being prepared for the coroner as police investigate the incident.

In nearby Gregory Hills, a 19-year-old man was arrested and hospitalised after crashing a motorcycle.

Police tried to pull him over about 12.45am but he allegedly did not stop and a pursuit began.

Officers lost sight of the motorcycle for a short time before finding it crashed on Gregory Hills Drive.

The 19-year-old was arrested and taken to Campbelltown Hospital in a stable condition for assessment and mandatory testing.

Australian Associated Press