A cyclist has died in a collision with a bus in Sydney's west, the latest in a series of serious bicycle crashes across the city this week.

Police said the 34-year-old male cyclist suffered critical injuries in the crash on the corner of Carlisle and Kurrajong avenues in Mount Druitt about 5pm on Thursday.

The man was taken to Westmead Hospital, but died that night.

Police are still investigating the cause of the crash, but say the cyclist and the bus were believed to be heading east on Kurrajong Avenue when the crash occurred as the bus turned on to Carlisle Avenue.

The male bus driver was not injured in the crash. He was taken to Mount Druitt Hospital for mandatory blood and urine testing, and will be interviewed by police.